Image coding method, image decoding method, image coding apparatus, image decoding apparatus, and image coding and decoding apparatus

ABSTRACT

An image coding method includes: writing, into a sequence parameter set, buffer description defining information for defining a plurality of buffer descriptions; writing, into the sequence parameter set, reference list description defining information for defining a plurality of reference list descriptions corresponding to the buffer descriptions; and writing, into a first header of each processing unit which is included in a coded bitstream, buffer description selecting information for specifying a selected buffer description.

FIELD

One or more exemplary embodiments disclosed herein relate generally toimage coding methods, image decoding methods, image coding apparatuses,image decoding apparatuses, and image coding and decoding apparatuses,and particularly to an image coding method and an image decoding methodeach of which uses a buffer description for specifying a picture to beheld in a buffer and a reference list description for specifying apicture to be referred to.

BACKGROUND

State-of-the-art video coding schemes, such as MPEG-4 AVC/H.264 (see NonPatent Literature 1) and the upcoming HEVC (High-Efficiency VideoCoding), perform coding of image or video content using inter-pictureprediction from previously coded or decoded reference pictures. In otherwords, the video coding schemes exploit the information redundancyacross consecutive pictures in time. In MPEG-4 AVC video coding scheme,reference pictures in the decoded picture buffer (DPB) are managedeither using a predefined sliding-window scheme for removing earlierpictures in coding order from the DPB, or explicitly using a number ofbuffer management signals in the coded bitstream to manage and removeunused reference pictures.

CITATION LIST Non Patent Literature

-   [Non Patent Literature 1] ISO/IEC 14496-10 “MPEG-4 Part10 Advanced    Video Coding”

SUMMARY Technical Problem

In the image coding method and the image decoding method which adoptsuch video coding schemes, there is a demand for a further improvementin coding efficiency.

Thus, one or more exemplary embodiments provide an image coding methodor an image decoding method in which the coding efficiency can improve.

Solution to Problem

In one general aspect, the techniques disclosed herein feature an imagecoding method for generating a coded bitstream by coding an image using(i) a buffer description for specifying a picture to be held in a bufferand (ii) a reference list description for specifying a picture to bereferred to, the image coding method comprising: writing, into asequence parameter set, buffer description defining information fordefining a plurality of buffer descriptions; writing, into the sequenceparameter set, reference list description defining information fordefining a plurality of reference list descriptions corresponding to thebuffer descriptions; selecting, for each processing unit that is apicture or a slice, one of the buffer descriptions, and writing, into afirst header of the processing unit, buffer description selectinginformation for specifying the selected buffer description, the firstheader being included in the coded bitstream; and coding the processingunit using the selected buffer description and one of the reference listdescriptions which corresponds to the selected buffer description.

These general and specific aspects may be implemented using a system, amethod, an integrated circuit, a computer program, or acomputer-readable recording medium such as a CD-ROM, or any combinationof systems, methods, integrated circuits, computer programs, orcomputer-readable recording media.

Additional benefits and advantages of the disclosed embodiments will beapparent from the Specification and Drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the Specification and Drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

Advantageous Effects

One or more exemplary embodiments or features disclosed herein providean image coding method or an image decoding method in which the codingefficiency can improve.

BRIEF DESCRIPTION OF DRAWINGS

These and other advantages and features will become apparent from thefollowing description thereof taken in conjunction with the accompanyingDrawings, by way of non-limiting examples of embodiments disclosedherein.

FIG. 1 shows an example of a picture referencing structure.

FIG. 2 shows a structure of a coded bitstream.

FIG. 3 is a block diagram of an image coding apparatus according to thefirst embodiment of the present disclosure.

FIG. 4 is a flowchart of an image coding method according to the firstembodiment of the present disclosure.

FIG. 5 is a flowchart of a writing process of reference list descriptiondefining information according to the first embodiment of the presentdisclosure.

FIG. 6 is a flowchart of the first example of a coding process accordingto the first embodiment of the present disclosure.

FIG. 7 is a flowchart of the second example of the coding processaccording to the first embodiment of the present disclosure.

FIG. 8A shows a structure of a coded bitstream according to the firstembodiment of the present disclosure.

FIG. 8B shows a structure of a coded bitstream according to a variationof the first embodiment of the present disclosure.

FIG. 9 shows a syntax structure of a sequence parameter set according tothe first embodiment of the present disclosure.

FIG. 10 is a block diagram of an image decoding apparatus according tothe first embodiment of the present disclosure.

FIG. 11 is a flowchart of an image decoding method according to thefirst embodiment of the present disclosure.

FIG. 12 is a flowchart of a process of obtaining the reference listdescription defining information according to the first embodiment ofthe present disclosure.

FIG. 13 is a flowchart of the first example of a decoding processaccording to the first embodiment of the present disclosure.

FIG. 14 is a flowchart of the second example of the decoding processaccording to the first embodiment of the present disclosure.

FIG. 15 is a flowchart of an image coding method according to the secondembodiment of the present disclosure.

FIG. 16 is a flowchart of a writing process of reference listdescription updating information according to the second embodiment ofthe present disclosure.

FIG. 17A shows a structure of a coded bitstream according to the secondembodiment of the present disclosure.

FIG. 17B shows a structure of a coded bitstream according to a variationof the second embodiment of the present disclosure.

FIG. 18 shows a syntax structure of a sequence parameter set accordingto the second embodiment of the present disclosure.

FIG. 19 is a flowchart of an image decoding method according to thesecond embodiment of the present disclosure.

FIG. 20 is a flowchart of a process of obtaining the reference listdescription updating information according to the second embodiment ofthe present disclosure.

FIG. 21 is a flowchart of an image coding method according to the thirdembodiment of the present disclosure.

FIG. 22A shows a structure of a coded bitstream according to the thirdembodiment of the present disclosure.

FIG. 22B shows a structure of a coded bitstream according to a variationof the third embodiment of the present disclosure.

FIG. 23 shows a syntax structure of a sequence parameter set accordingto the third embodiment of the present disclosure.

FIG. 24 is a flowchart of an image decoding method according to thethird embodiment of the present disclosure.

FIG. 25 is a flowchart of an image coding method according to the fourthembodiment of the present disclosure.

FIG. 26 shows a structure of a coded bitstream according to the fourthembodiment of the present disclosure.

FIG. 27 shows a syntax structure of a slice header according to thefourth embodiment of the present disclosure.

FIG. 28 is a flowchart of an image decoding method according to thefourth embodiment of the present disclosure.

FIG. 29 shows an overall configuration of a content providing system forimplementing content distribution services.

FIG. 30 shows an overall configuration of a digital broadcasting system.

FIG. 31 shows a block diagram illustrating an example of a configurationof a television.

FIG. 32 shows a block diagram illustrating an example of a configurationof an information reproducing/recording unit that reads and writesinformation from and on a recording medium that is an optical disk.

FIG. 33 shows an example of a configuration of a recording medium thatis an optical disk.

FIG. 34A shows an example of a cellular phone.

FIG. 34B is a block diagram showing an example of a configuration of acellular phone.

FIG. 35 illustrates a structure of multiplexed data.

FIG. 36 schematically shows how each stream is multiplexed inmultiplexed data.

FIG. 37 shows how a video stream is stored in a stream of PES packets inmore detail.

FIG. 38 shows a structure of TS packets and source packets in themultiplexed data.

FIG. 39 shows a data structure of a PMT.

FIG. 40 shows an internal structure of multiplexed data information.

FIG. 41 shows an internal structure of stream attribute information.

FIG. 42 shows steps for identifying video data.

FIG. 43 is a block diagram showing an example of a configuration of anintegrated circuit for implementing the moving picture coding method andthe moving picture decoding method according to each of embodiments.

FIG. 44 shows a configuration for switching between driving frequencies.

FIG. 45 shows steps for identifying video data and switching betweendriving frequencies.

FIG. 46 shows an example of a look-up table in which video datastandards are associated with driving frequencies.

FIG. 47A is a diagram showing an example of a configuration for sharinga module of a signal processing unit.

FIG. 47B is a diagram showing another example of a configuration forsharing a module of the signal processing unit.

DESCRIPTION OF EMBODIMENTS

(Underlying Knowledge Forming Basis of the Present Disclosure)

Recent developments in the HEVC video coding scheme include theintroduction of DPB management using buffer descriptions. A bufferdescription defines the pictures that are retained in the DPB, insteadof defining the pictures that are to be removed from the DPB. In otherwords, a buffer description is a list of picture identifiers indicatingall reference pictures stored in the DPB. Each item in this list isreferred to as a buffer element. A buffer element contains a pictureidentifier unique to each picture, such as a picture order count (POC)number, and additional information of the picture such as a temporal_idvalue.

This buffer description is activated at the start of coding or decodingof a picture. Pictures that are not included in the active bufferdescription are removed from the DPB. Benefits of this bufferdescriptions include improved robustness against transmission/deliverylosses and simplified handling of non-existent pictures.

In some cases, multiple pictures in a video sequence share the samepicture referencing structure. For example, a low delay coding structureuses a periodic clustering structure in which the same layer structureis periodically repeated in unit of four pictures as shown in FIG. 1 .This repeating unit (that is four pictures herein) is called a cluster.

In the example shown in FIG. 1 , the picture numbers (P0 to P12)indicate both unique coding order and unique display or output order ofpictures. The pictures P0, P4, P8 and P12 constitute the first layer ofpictures. There pictures are coded with the highest quality, forexample, by applying quantization least strongly. Pictures P2, P6 andP10 constitute the second layer. These pictures are coded with lowerquality than the first layer. Pictures P1, P3, P5, P7, P9 and P11constitute the third layer. These pictures are coded with the lowestquality. In such a periodic referencing structure, pictures located atthe same relative position within their clusters (for example P1, P5 andP9) usually use the same relative picture referencing structure. Forexample, the picture P5 uses the pictures P4 and P2 as referencepictures, while the picture P9 uses the pictures P8 and P6 as referencepictures.

In order to accommodate periodic clustering structures such as the abovestructure, a conceivable approach is periodic signaling of bufferdescriptions. This buffer description specifies the temporal distancesor positions of the reference pictures relative to a target picture tobe coded or decoded. By so doing, the reference pictures stored in theDPB can be specified. For example, this buffer description is signalledonce in the picture parameter set (PPS). This buffer description is thenreferred to repeatedly in the slice headers of the pictures having thesame relative position within a cluster. For example, a bufferdescription specifying relative positions of {−1, −3} can be used inboth P5 to specify {P4, P2} as reference pictures and by P9 to specify{P8, P6} as reference pictures.

FIG. 2 shows an example of the signaling structure of buffer descriptionin this case. A coded bitstream 500 shown in FIG. 2 includes a sequenceparameter set (SPS) 501 (SPS0), a plurality of picture parameter sets(PPSs) 502 (PPS0 and PPS1), and a plurality of picture data 503. Each ofthe picture data 503 includes a plurality of slice data 535. Each of theslice data 535 includes a slice header 541 and a slice data part 542.The slice data part 542 includes a plurality of coding unit (CU) data543.

Each of the PPSs 502 includes a PPS identifier 522 (pps_id) and bufferdescription defining information 512 (BD define). The buffer descriptiondefining information 512 indicates a plurality of buffer descriptions515 (BD0 to BDn). Each of the buffer descriptions 515 includes aplurality of buffer elements 515A (BE0 to BE2).

Thus, the plurality of buffer descriptions 515 are defined using thebuffer description defining information 512 in the picture parametersets 502. Each of the PPSs 502 is identified by a PPS identifier 522unique to the PPS.

The slice header 541 includes PPS selecting information 533 (pps_select)and buffer description updating information 523 (BD update).

The PPS selecting information 533 indicates the PPS 502 referred toduring coding or decoding of the slice. In the example in FIG. 2 ,pps_select=0 is satisfied, and the PPS0 having pps_id=0 is selected.

The buffer description updating information 523 includes informationwhich specifies the buffer description selected out of the bufferdescriptions 515. In the example in FIG. 2 , the buffer description BD1is selected. Additionally, the buffer description updating information523 includes buffer description modification information. The bufferdescription modification information assigns a picture identifier to aselected buffer element 515A within the selected buffer description 515.Here, the picture identifier is specified either using relative positionor using an identifier unique to the picture. The identifier unique tothe picture includes, for example, the picture order count (POC) number.In the example in FIG. 2 , the picture P₂₁₄ identified by its POCnumber=214 is assigned to the buffer element BE0 within the bufferdescription BD1. This modification applies only to the current targetslice and does not apply to subsequent slices.

In a coded bitstream, reference pictures used for the inter predictionprocess of prediction units (an N×N block) are identified usingreference indexes. All available reference pictures and their associatedreference indexes are described in a reference list. When bi-predictiveinter prediction is used, two reference lists are used for describingtwo groups of reference pictures and the associated reference indexes.Smaller reference indexes are represented with fewer bits in the codedbitstream compared to larger reference indexes. Therefore, higher codingefficiency is achieved by assigning smaller reference indexes tofrequently used reference pictures.

At the start of the coding or decoding of a slice, a default referencelist is constructed by assigning indexes to all available referencepictures according to a predetermined ordering scheme. The image codingapparatus may further reorder the reference indexes included in thedefault reference list and write reference list reordering informationinto the slice header in the coded bitstream. The reordered referencelist applies only to the current target slice and does not apply tosubsequent slices.

Here, the inventors found that the above technique has a problem thatthe information (parameters) for describing reference list reordering isonly applied once in a current slice to be coded or decoded. However, asdescribed above, multiple pictures in a video sequence share the samereferencing structure in some cases. Consequently, information fordescribing the same reference list reordering process is signalledrepeatedly in the coded bitstream.

Thus, the inventors found the problem of a decrease in coding efficiencywhich is due to repeated information included in the coded bitstream.

According to an exemplary embodiment disclosed herein, an image codingmethod for generating a coded bitstream by coding an image using (i) abuffer description for specifying a picture to be held in a buffer and(ii) a reference list description for specifying a picture to bereferred to, comprises: writing, into a sequence parameter set, bufferdescription defining information for defining a plurality of bufferdescriptions; writing, into the sequence parameter set, reference listdescription defining information for defining a plurality of referencelist descriptions corresponding to the buffer descriptions; selecting,for each processing unit that is a picture or a slice, one of the bufferdescriptions, and writing, into a first header of the processing unit,buffer description selecting information for specifying the selectedbuffer description, the first header being included in the codedbitstream; and coding the processing unit using the selected bufferdescription and one of the reference list descriptions which correspondsto the selected buffer description.

By so doing, in the image coding method according to an exemplaryembodiment disclosed herein, the buffer description defining informationand the reference list description defining information are written intothe sequence parameter set shared by a plurality of pictures, and abuffer description identifier indicating a buffer description to beselected is written into a header of each picture or slice. This allowsa reduction in redundant information and thereby allows an improvementin coding efficiency in the image coding method as compared to the casewhere the buffer description defining information and the reference listdescription defining information are written into a picture parameterset.

For example, the image coding method comprises: modifying at least oneof the buffer descriptions, and writing, into a second header of theprocessing unit, buffer description updating information for indicatingdetails of the modification; and writing, into the second header,reference list description updating information for defining a referencelist description which corresponds to the modified buffer description,wherein, in the coding, the processing unit is coded using (i) themodified buffer description and (ii) the reference list descriptionwhich corresponds to the modified buffer description.

By so doing, in the image coding method, the buffer description and thereference list description set in the sequence parameter set can beupdated for each picture or slice. Thus, the image coding method allowsa reduction in redundant information and also allows, when necessary,the buffer description and the reference list description to be modifiedfor each picture or slice.

For example, the second header is a picture parameter set, the firstheader is a picture header or a slice header, and in the selecting, whenat least one of the buffer descriptions is modified, one bufferdescription is selected out of a plurality of buffer descriptionsincluding the modified buffer description.

For example, the first header and the second header are a slice header,and in the modifying, the selected buffer description is modified as theat least one of the buffer descriptions.

For example, the first header and the second header are a pictureparameter set, in the modifying and the writing, the selected bufferdescription is modified as the at least one of the buffer descriptions,and the buffer description updating information is written into a firstpicture parameter set that is one of picture parameter sets included inthe coded bitstream, in the writing of reference list descriptionupdating information, the reference list description updatinginformation is written into the first picture parameter set, and in theselecting and the writing, the buffer description selecting informationis written into the first picture parameter set, and picture parameterset selecting information for specifying the first picture parameter setout of the picture parameter sets is written into a header of theprocessing unit.

For example, the reference list description defining informationincludes: a first reordering flag for indicating whether or notreordering of a reference list is performed; and first reference listreordering information for indicating details of the reordering, and thewriting of reference list description defining information includes:writing the first reordering flag into the sequence parameter set;judging using the first reordering flag whether or not the reordering ofthe reference list is performed; and writing the first reference listreordering information into the sequence parameter set when thereordering of the reference list is performed.

For example, the reference list description updating informationincludes: a reordering flag for indicating whether or not reordering ofa reference list is performed; and reference list reordering informationfor indicating details of the reordering, and the writing of referencelist description updating information includes: writing the reorderingflag into the second header; judging using the reordering flag whetheror not the reordering of the reference list is performed; and writingthe reference list reordering information into the second header whenthe reordering of the reference list is performed.

For example, the coding includes: constructing, according to apredetermined default reference list description, a reference listincluding picture identifiers of all pictures indicated in the selectedbuffer description; judging using the first reordering flag whether ornot reordering of the constructed reference list is performed;reordering, according to the first reference list reorderinginformation, the picture identifiers in the reference list when thereordering of the reference list is performed; and coding a currentslice using the reordered reference list.

For example, the coding includes: constructing, according to apredetermined default reference list description, a reference listincluding picture identifiers of all pictures indicated in the selectedbuffer description; writing, into a slice header of a current slice, anupdate flag for indicating whether or not the reference list descriptionwhich corresponds to the selected buffer description is updated; judgingusing the update flag whether or not the reference list description isupdated; writing, into the slice header, a second reordering flag forindicating whether or not reordering of the reference list is performedwhen the reference list description is updated; judging using the secondreordering flag whether or not the reordering of the reference list isperformed; writing, into the slice header, second reference listreordering information for indicating details of the reordering of thereference list when the reordering is performed; reordering the pictureidentifiers in the reference list according to the second reference listreordering information; judging using the first reordering flag whetheror not the reordering of the reference list is performed when thereference list description is not updated; reordering, according to thefirst reference list reordering information, the picture identifiers inthe reference list when the reordering of the reference list isperformed; and coding the current slice using the reordered referencelist.

Furthermore, according to an exemplary embodiment disclosed herein, animage decoding method for decoding a coded bitstream using (i) a bufferdescription for specifying a picture to be held in a buffer and (ii) areference list description for specifying a picture to be referred to,comprises: obtaining, from a sequence parameter set corresponding to thecoded bitstream, buffer description defining information for defining aplurality of buffer descriptions; obtaining, from the sequence parameterset, reference list description defining information for defining aplurality of reference list descriptions corresponding to the bufferdescriptions; obtaining, from a first header of a processing unit thatis a picture or a slice, buffer description selecting information forspecifying one of the buffer descriptions, the first header beingincluded in the coded bitstream; and decoding the processing unit using(i) a buffer description specified in the buffer description selectinginformation and (ii) one of the reference list descriptions whichcorresponds to the specified buffer description.

By so doing, a bitstream coded with improved coding efficiency can bedecoded in the image decoding method according to an exemplaryembodiment disclosed herein.

For example, the image decoding method further comprises: obtaining,from a second header of the processing unit, buffer description updatinginformation for indicating details of modification of at least one ofthe buffer descriptions, the second header being included in the codedbitstream; and obtaining, from the second header, reference listdescription updating information for defining a reference listdescription which corresponds to the modified buffer description,wherein, in the decoding, the at least one of the buffer descriptions ismodified according to the details of modification indicated in thebuffer description updating information, and the processing unit isdecoded using (i) the modified buffer description and (ii) the referencelist description which corresponds to the modified buffer description.

For example, the second header is a picture parameter set, and the firstheader is a picture header or a slice header.

For example, the first header and the second header are a slice header.

For example, the first header and the second header are a pictureparameter set, and in the obtaining of buffer description selectinginformation, picture parameter set selecting information for specifyingone of picture parameter sets included in the coded bitstream isobtained from a header of the processing unit, and the bufferdescription selecting information is obtained from a picture parameterset specified in the picture parameter set selecting information.

For example, the reference list description defining informationincludes: a first reordering flag for indicating whether or notreordering of a reference list is performed; and first reference listreordering information for indicating details of the reordering, and theobtaining of reference list description defining information includes:obtaining the first reordering flag; judging using the first reorderingflag whether or not the reordering of the reference list is performed;and obtaining the first reference list reordering information when thereordering of the reference list is performed.

For example, the reference list description updating informationincludes: a reordering flag for indicating whether or not reordering ofa reference list is performed; and reference list reordering informationfor indicating details of the reordering, and the obtaining of referencelist description updating information includes: obtaining the reorderingflag from the second header; judging using the reordering flag whetheror not the reordering of the reference list is performed; and obtaining,from the second header, the reference list reordering information whenthe reordering of the reference list is performed.

For example, the decoding includes: constructing, according to apredetermined default reference list description, a reference listincluding picture identifiers of all pictures indicated in the selectedbuffer description; judging using the first reordering flag whether ornot reordering of the constructed reference list is performed;reordering, according to the first reference list reorderinginformation, the picture identifiers in the reference list when thereordering of the reference list is performed; and decoding a currentslice using the reordered reference list.

For example, the decoding includes: constructing, according to apredetermined default reference list description, a reference listincluding picture identifiers of all pictures indicated in the selectedbuffer description; obtaining, from a slice header of a current slice,an update flag for indicating whether or not the reference listdescription which corresponds to the selected buffer description isupdated; judging using the update flag whether or not the reference listdescription is updated; obtaining, from the slice header, a secondreordering flag for indicating whether or not reordering of thereference list is performed when the reference list description isupdated; judging using the second reordering flag whether or not thereordering of the reference list is performed; obtaining, from the sliceheader, second reference list reordering information for indicatingdetails of the reordering of the reference list when the reordering isperformed; reordering the picture identifiers in the reference listaccording to the second reference list reordering information; judgingusing the first reordering flag whether or not the reordering of thereference list is performed when the reference list description is notupdated; reordering, according to the first reference list reorderinginformation, the picture identifiers in the reference list when thereordering of the reference list is performed; and decoding the currentslice using the reordered reference list.

Furthermore, according to an exemplary embodiment disclosed herein, animage coding apparatus for generating a coded bitstream by coding animage using (i) a buffer description for specifying a picture to be heldin a buffer and (ii) a reference list description for specifying apicture to be referred to, comprises a frame memory control unitconfigured to perform the following: writing, into a sequence parameterset, buffer description defining information for defining a plurality ofbuffer descriptions; writing, into the sequence parameter set, referencelist description defining information for defining a plurality ofreference list descriptions corresponding to the buffer descriptions;and selecting, for each processing unit that is a picture or a slice,one of the buffer descriptions, and writing, into a first header of theprocessing unit, buffer description selecting information for specifyingthe selected buffer description, the first header being included in thecoded bitstream, wherein the image coding apparatus codes the processingunit using the selected buffer description and one of the reference listdescriptions which corresponds to the selected buffer description.

By so doing, the image coding apparatus according to an exemplaryembodiment disclosed herein writes the buffer description defininginformation and the reference list description defining information intothe sequence parameter set shared by a plurality of pictures, andwrites, into a header of each picture or slice, a buffer descriptionidentifier indicating a buffer description to be selected. This allowsthe image coding apparatus to reduce redundant information and therebyimprove the coding efficiency as compared to the case where the bufferdescription defining information and the reference list descriptiondefining information are written into a picture parameter set.

Furthermore, according to an exemplary embodiment disclosed herein, animage decoding apparatus for decoding a coded bitstream using (i) abuffer description for specifying a picture to be held in a buffer and(ii) a reference list description for specifying a picture to bereferred to, comprises a frame memory control unit configured to performthe following: writing, into a sequence parameter set, bufferdescription defining information for defining a plurality of bufferdescriptions; writing, into the sequence parameter set, reference listdescription defining information for defining a plurality of referencelist descriptions corresponding to the buffer descriptions; andselecting, for each processing unit that is a picture or a slice, one ofthe buffer descriptions, and writing, into a first header of theprocessing unit, buffer description selecting information for specifyingthe selected buffer description, the first header being included in thecoded bitstream, wherein the image coding apparatus codes the processingunit using the selected buffer description and one of the reference listdescriptions which corresponds to the selected buffer description.

This allows the image decoding apparatus according to an exemplaryembodiment disclosed herein to decode a bitstream coded with theimproved coding efficiency.

Furthermore, according to an exemplary embodiment disclosed herein, animage coding and decoding apparatus comprises the image coding apparatusand the image decoding apparatus.

These general and specific aspects may be implemented using a system, amethod, an integrated circuit, a computer program, or acomputer-readable recording medium such as a CD-ROM, or any combinationof systems, methods, integrated circuits, computer programs, orcomputer-readable recording media.

Hereinafter, exemplary embodiments are described in greater detail withreference to the accompanying Drawings.

Each of the exemplary embodiments described below shows a general orspecific example. The numerical values, shapes, materials, structuralelements, the arrangement and connection of the structural elements,steps, the processing order of the steps etc. shown in the followingexemplary embodiments are mere examples, and therefore do not limit theinventive concept disclosed herein. Therefore, among the structuralelements in the following exemplary embodiments, structural elements notrecited in any one of the independent claims defining the most genericpart of the inventive concept are described as arbitrary structuralelements.

Four embodiments are described in the following. It will be apparent tothose skilled in the art that combinations of these embodiments can becarried out to further increase the usability and adaptability ofperiodic reference list descriptions.

First Embodiment

In this embodiment, buffer description defining information andreference list description defining information are written into SPS.This allows a reduction in redundant information and thereby allows animprovement in coding efficiency as compared to the case where thebuffer description defining information and the reference listdescription information are written into a picture parameter set.

[Coding Apparatus]

FIG. 3 is a block diagram which shows a structure of an image codingapparatus 100 according to this embodiment.

The image coding apparatus 100 codes an input image signal 120 on ablock-by-block basis so as to generate a coded bitstream 132. As shownin FIG. 3 , the image coding apparatus 100 includes a subtractor 101, anorthogonal transformation unit 102, a quantization unit 103, an inversequantization unit 104, an inverse orthogonal transformation unit 105, anadder 106, a block memory 107, a frame memory 108, an intra predictionunit 109, an inter prediction unit 110, a picture type determinationunit 111, a variable-length coding unit 112, and a frame memory controlunit 113.

The input image signal 120 is a video or image bitstream. The subtractor101 calculates a difference between prediction image data 131 and theinput image signal 120, thereby generating prediction error data 121.The orthogonal transformation unit 102 performs orthogonaltransformation on the prediction error data 121 to generate frequencycoefficients 122. The quantization unit 103 quantizes the frequencycoefficients 122, thereby generating quantized values 123. Thevariable-length coding unit 112 performs entropy coding (variable-lengthcoding) on the quantized values 123, thereby generating the codedbitstream 132.

The inverse quantization unit 104 inversely quantizes the quantizedvalues 123, thereby generating frequency coefficients 124. The inverseorthogonal transformation unit 105 performs inverse orthogonaltransformation on the frequency coefficients 122, thereby generatingprediction error data 125. The adder 106 adds the prediction error data125 and the prediction image data 131, thereby generating decoded imagedata 126. The block memory 107 holds the decoded image data 126 asdecoded image data 127 on a block-by-block basis. The frame memory 108holds the decoded image data 126 as decoded image data 128 on aframe-by-frame basis.

The intra prediction unit 109 performs intra prediction to generateprediction image data 129 of a current block to be coded. Specifically,the intra prediction unit 109 searches within the decoded image data 127stored in the block memory 107, and estimates an image area which ismost similar to the input image signal 120.

The inter prediction unit 110 performs inter prediction using theper-frame decoded image data 128 stored in the frame memory 108, togenerate prediction image data 130 of the current block.

The picture type determination unit 111 selects one of the predictionimage data 129 and the prediction image data 130 and outputs theselected data as the prediction image data 131.

The frame memory control unit 113 manages the decoded image data 128stored in the frame memory 108. Specifically, the frame memory controlunit 113 determines whether the decoded image data 128 is kept in theframe memory 208 or removed from the frame memory 208. Furthermore, theframe memory control unit 113 constructs reference lists to be used bythe inter prediction unit 110. Furthermore, the frame memory controlunit 113 generates frame memory control information 133 which includesthe buffer description defining information and the reference listdescription defining information. The variable-length coding unit 112generates the coded bitstream 132 which includes this frame memorycontrol information 133.

[Coding Process]

Next, a description is given to an image coding method which isperformed by the image coding apparatus 100 as mentioned above.

FIG. 4 is a flowchart of an image coding method according to thisembodiment. Furthermore, FIG. 4 shows a coding process which isperformed on a single video sequence including a plurality of pictures.

Firstly, the image coding apparatus 100 determines a plurality of bufferdescriptions and the reference list descriptions corresponding to theplurality of buffer descriptions which are to be used over a pluralityof pictures in a video sequence (S101). The buffer descriptions are usedto specify pictures to be held in the buffer (frame memory).Specifically, each of the buffer descriptions includes a plurality ofbuffer elements. Each buffer element contains a unique pictureidentifier corresponding to one reference picture stored in the framememory. This means that each of the buffer descriptions indicates aplurality of reference pictures stored in the frame memory.

The reference list descriptions are used to specify pictures to bereferred to. Specifically, each reference list description correspondsexclusively (one-to-one) to one buffer description. The reference listdescriptions are used to generate a reference list indicating acorrespondence relationship between reference pictures and referenceindexes. Specifically, each of the reference list descriptions describesthe reference indexes and the associated reference pictures in thereference lists. These reference indexes are written into a codedbitstream as information which indicates the reference pictures actuallyreferred to and are thus transmitted from the image coding apparatus 100to an image decoding apparatus. One reference list is used whenuni-directional prediction is used, while two reference lists are usedwhen bi-directional prediction is used.

Next, the image coding apparatus 100 writes, into a sequence parameterset (SPS) in the coded bitstream 132, the buffer description defininginformation which defines the determined buffer descriptions (S102).Here, SPS is a parameter set (header information) in each videosequence.

Next, the image coding apparatus 100 writes, into SPS, the referencelist defining information for defining the plurality of reference listdescriptions (S103).

Next, the image coding apparatus 100 selects, for each picture, one ofthe buffer descriptions which is to be used to code the picture (S104).It is to be noted that the image coding apparatus 100 may select onebuffer description for each slice.

Next, the image coding apparatus 100 writes the buffer descriptionselecting information which specifies the selected buffer descriptioninto a picture header corresponding to the current picture (or a sliceheader corresponding to the current slice) and included in the codedbitstream 132 (S105). In addition, one reference list descriptioncorresponding to the selected buffer description is selected.

Finally, the image coding apparatus 100 codes a current picture or sliceusing the buffer description selected for the picture or slice and thereference list description corresponding to the buffer description(S106). Furthermore, the image coding apparatus 100 generates the codedbitstream 132 which includes the resulting coded data.

The following describes a process of writing the reference listdescription defining information (S103) shown in FIG. 4 . FIG. 5 is aflowchart of a writing process (S103) of reference list descriptiondefining information.

In this embodiment, the reference list description defining informationis written into SPS of the coded bitstream 132 in this writing process(S103).

Firstly, the image coding apparatus 100 determines whether a defaultreference list or a reordered reference list is used (S111). Here, thedefault reference list is a reference list which is constructedaccording to a predetermined default reference list constructing schemein the image coding apparatus and the image decoding apparatus. In otherwords, as the default reference list for the same picture (or slice),the same reference list is constructed in the image coding apparatus andthe image decoding apparatus.

Next, the image coding apparatus 100 writes, into SPS, a firstreordering flag for indicating whether or not reference list reorderingis performed (S112). The image coding apparatus 100 then judges usingthe written first reordering flag whether or not reference listreordering is performed (S113).

When reference list reordering is performed (Yes in S113), the imagecoding apparatus 100 writes, into SPS, first reference list reorderinginformation for reordering picture identifiers in a reference list(S114) and terminates the writing process (S103). In other words, thefirst reference list reordering information indicates the details ofreordering of the picture identifiers.

On the other hand, when reference list reordering is not performed (Noin S113), the image coding apparatus 100 terminates the writing process(S103).

Thus, the reference list description defining information includes thefirst reordering flag and the first reference list reorderinginformation.

The following describes a coding process (S106) shown in FIG. 4 . FIG. 6is a flowchart which shows a first embodiment of the coding process(S106).

Firstly, the image coding apparatus 100 constructs a default referencelist comprising all picture identifiers in the selected bufferdescription according to a default reference list constructing scheme(S121). Next, the image coding apparatus 100 judges using a firstreordering flag included in the reference list description defininginformation whether or not reference list reordering is performed(S122).

When reference list reordering is performed (Yes in S123), the imagecoding apparatus 100 reorders the picture identifiers in the referencelist according to reference list reordering information included in thereference list description defining information (S124). The image codingapparatus 100 then codes the current picture or slice using thereordered reference list (S125).

On the other hand, when reference list reordering is not performed (Noin S123), the image coding apparatus 100 codes the current picture orslice using the default reference list (S125).

FIG. 7 is a flowchart which shows a second embodiment of the codingprocess (S106).

Firstly, the image coding apparatus 100 constructs a default referencelist comprising all picture identifiers in the selected bufferdescription according to a default reference list constructing scheme(S131). Next, the image coding apparatus 100 determines whether or not areference list description is updated (reference list descriptionoverride is used) (S132). Here, update (override) means modifying, in alower layer, the reference list description defined in an upper layer.Specifically, the update (override) is to modify, for each picture orslice, the reference list description defined in the reference listdescription defining information in SPS.

Next, the image coding apparatus 100 writes, into a slice header of thecurrent slice, an update flag for indicating whether or not a referencelist description is updated (S133). The image coding apparatus 100 thenjudges using the update flag whether or not a reference list descriptionis updated (S134).

When a reference list description is updated (Yes in S134), the imagecoding apparatus 100 writes, into the slice header of the current slice,a second reordering flag for indicating whether or not reference listreordering is performed (S135). The image coding apparatus 100 thenjudges using the second reordering flag whether or not reference listreordering is performed (S136).

When reference list reordering is performed (Yes in S136), the imagecoding apparatus 100 writes, into the slice header of the current slice,second reference list reordering information for reordering pictureidentifiers in the reference list (S137). The image coding apparatus 100then reorders the picture identifiers in the reference list according tothe second reference list reordering information (S138).

Next, the image coding apparatus 100 codes the current slice using thereordered reference list (S142).

On the other hand, when a reference list description is not updated (Noin S134), the image coding apparatus 100 judges using the firstreordering flag included in the reference list description defininginformation whether or not reference list reordering is performed (S139and S140).

When reference list reordering is performed (Yes in S140), the imagecoding apparatus 100 reorders the picture identifiers in the referencelist according to the first reference list reordering informationincluded in the reference list description defining information (S141).

Next, the image coding apparatus 100 codes the current slice using thereordered reference list (S142).

On the other hand, when reference list reordering is not performed (Noin S136 or No in S140), the image coding apparatus 100 codes the currentslice using the default reference list (S142).

[Syntax Diagram]

FIGS. 8A and 8D are each a syntax diagram which shows the locations ofthe buffer description defining information and the reference listdescription defining information in a coded bitstream in thisembodiment. Two exemplary syntax locations are described in thefollowing.

The coded bitstream 132 shown in FIG. 8A includes SPS 301 (SPS0), aplurality of PPSs 302 (PPS0 and PPS1), and a plurality of picture data303. Each of the picture data 303 includes a picture header 331 and apicture data part 332. The picture data part 332 includes a plurality ofslice data 335.

The SPS 301 includes buffer description defining information 312 (BDdefine), reference list description defining information 313 (RLDdefine), and an SPS identifier 311 (sps_id).

The buffer description defining information 312 defines a plurality ofbuffer descriptions 315. For example, like the above-mentioned bufferdescriptions 515, the buffer descriptions 315 each include a pluralityof buffer elements. Furthermore, the buffer description defininginformation 312 includes the number of buffer descriptions 314(number_of_bds) indicating the number of buffer descriptions 315included in the buffer description defining information 312.

The reference list description defining information 313 defines aplurality of reference list descriptions 316. Each reference listdescription 316 (e.g. RLD2) is associated exclusively with a bufferdescription 315 (e.g. BD2). Furthermore, the SPS 301 is identified bythe unique SPS identifier 311 (e.g. sps_id=0).

Each of the PPSs 302 includes SPS selecting information 321 (sps_select)and a PPS identifier 322 (pps_id). The SPS selecting information 321(e.g. sps_select=0) indicates the SPS301 which is referred to.Furthermore, each of the PPSs 302 is identified by the unique PPSidentifier 322 (e.g. pps_id=0).

The picture header 331 includes PPS selecting information (pps_select)333 and buffer description selecting information 334 (bd_select).

PPS selecting information 333 (e.g. pps_select=0) indicates the PPS 302which is referred to. Using this PPS selecting information 333, one ofthe PPSs 302 is referred to from the picture header 331. Furthermore,using the SPS selecting information 321 included in the PPS 302, the SPS301 is referred to from the PPS 302 referred to. This links the currentpicture to the available plurality of buffer descriptions and referencelist descriptions defined in the SPS 301.

With the buffer description selecting information 334 (e.g.bd_select=2), one of the buffer descriptions is specified. Thus, onebuffer description and its corresponding reference list description areselected out of the plurality of buffer descriptions and reference listdescriptions.

The slice data 335 included in the picture data 303 is coded and decodedusing ordered reference pictures according to the selected bufferdescription and the selected reference list description.

Furthermore, as shown in FIG. 8B, each of the slice data 335 includes aslice header 341 and a slice data part 342. The slice data part 342includes a plurality of coding unit (CU) data 343.

In a coded bitstream 132A, the PPS selecting information 333 and thebuffer description selecting information 334 are not included in apicture header 331A, but are included in the slice header 341. Also inthis case, the effects the same as those in the case shown in FIG. 8Acan be obtained.

It is to be noted that “slice” in the above explanation may be replacedby “sub-picture unit”. The sub-picture unit includes, for example, atile, an entropy slice, and a group of blocks constituting a wavefrontprocessing sub-picture partition (Wavefront Parallel Processing (WPP)unit).

The above buffer description defining information and reference listdescription defining information are signalled in the SPS syntaxstructure according to the pseudo code in the table shown in FIG. 9 .

The descriptors define the parsing process of each syntax elementaccording to the same bit representation as the AVC video coding schemeas follows:

ue(v): unsigned integer Exp-Golomb-coded syntax element with the leftbit first.

u(n): unsigned integer using n bits. When n is “v” in the syntax table,the number of bits varies in a manner dependent on the value of othersyntax elements.

The following explains the semantics associated with the syntax elementsrepresenting the buffer description defining information and thereference list description defining information. The following syntaxelements are included in the SPS 301.

bits_for_temporal_id indicates the number of bits of first_temporal_idand temporal_id.

number_of_bds (the number of buffer descriptions 314) indicates thenumber of number_of_bes_minus1 included in the SPS 301. In other words,number_of_bds indicates the number of buffer descriptions 315 includedin the SPS 301.

number_of_bes_minus1[i] indicates the number of buffer elements in thebuffer description BD[i].

first_delta_poc_sign_flag[i] indicates the sign (plus or minus) of thePOC difference between a current picture and the reference pictureassociated with the buffer element BE[i][0] in the buffer descriptionBD[i]. first_delta_poc_sign_flag[i] equal to 0 specifies that the POCdifference has a positive value, while first_delta_poc_sign_flag[i]equal to 1 specifies that the POC difference has a negative value.

first_delta_poc_minus1[i] indicates an absolute POC difference valuebetween a current picture and the reference picture associated with thebuffer element BE[i][0] in the buffer description BD[i].first_delta_poc_sign_flag[i] and first_delta_poc[i] define the value ofthe signed variable BDDeltaPOC[i][0] asBDDeltaPOC[i][0]=(first_delta_poc_minus1[i]+1)*(1−2*first_delta_poc_sign_flag[i])

BDDeltaPOC[i][0] shall be the highest signed POC difference value amongall reference pictures associated with the buffer elements BE[i][j] inthe buffer description BD[i].

first_temporal_id[i] specifies a temporal identifier and is representedby bits_for_temporal_id bits. first_temporal_id[i] defines the value ofthe unsigned variable BDTemporalID[i][0] asBDTemporalID[i][0]=first_temporal_id[i].

delta_poc_minus1[i][j] indicates an negative POC distance value from thereference picture associated with the buffer element BE[i][j] toreference picture associated with the buffer element BE[i][j+1] in thebuffer description BD[i]. delta_poc_minus1[i][j] defines the value ofthe signed variable BDDeltaPOC[i][j+1] asBDDeltaPOC[i][j+1]=BDDeltaPOC[i][j]−(delta_poc_minus1[i][j]+1)

temporal_id[i][j] specifies a temporal identifier and is represented bybits_for_temporal_id bits. temporal_id[i] defines the value of theunsigned variable BDTemporalID[i][j+1] asBDTemporalID[i][j+1]=temporal_id[i][j]

ref_pic_list_modification_flag_l0[i] equal to 1 specifies thatnum_ref_idx_l0_active_minus1[i] and more_modification_flag are presentfor specifying the reference picture list RL0[i] corresponding to thebuffer description BD[i]. ref_pic_list_modification_flag_l0[i] equal to0 specifies that num_ref_idx_l0_active_minus1[i] andmore_modification_flag are not present.

When ref_pic_list_modification_flag_l0[i] is equal to 1, the number oftimes that more_modification_flag is equal to 1 followingref_pic_list_modification_flag_l0[i] shall not exceed(num_ref_idx_l0_active_minus1[i]+1).

ref_pic_list_modification_flag_l1[i] equal to 1 specifies thatnum_ref_idx_l1_active_minus1[i] and more_modification_flag are presentfor specifying the reference picture list RL1[i] corresponding to thebuffer description BD[i]. ref_pic_list_modification_flag_l1[i] equal to0 specifies that num_ref_idx_l1_active_minus1[i] andmore_modification_flag are not present.

When ref_pic_list_modification_flag_l1[i] is equal to 1, the number oftimes that more_modification_flag is equal to 1 followingref_pic_list_modification_flag_l1[i] shall not exceed(num_ref_idx_l1_active_minus1[i]+1).

num_ref_idx_l0_active_minus1[i] indicates the maximum reference indexfor reference picture list RL0[i] corresponding to the bufferdescription BD[i].

num_ref_idx_l1_active_minus1[i] indicates the maximum reference indexfor reference picture list RL1[i] corresponding to the bufferdescription BD[i].

more_modification_flag together with be_idx specifies which of thereference pictures are re-mapped. more_modification_flag equal to 1specifies that be_idx is present immediately followingmore_modification_flag. more_modification_flag equal to 0 specifies theend of the loop for re-mapping reference pictures in the referencepicture list.

be_idx_in_ref_pic_list indicates the reference picture associated withthe buffer element BE[i][be_idx] in the current buffer descriptionBD[i]. be_idx identifies the picture to be re-mapped in the currentreference list RL0[i] or RL1[i] associated with the buffer descriptionBD[i]. In this embodiment, the re-mapping process for reference picturesin a reference list is performed according to the same scheme as AVCvideo coding scheme.

The variables or lists BDDeltaPOC[i] and BDTemporalID[i] represent theplurality of periodic buffer descriptions BD[i]. One out of thisplurality of buffer descriptions is subsequently selected, and theselected buffer description is used in the slice coding and decodingprocess as mentioned above.

It is to be noted that the syntax loop describing buffer descriptiondefining information and reference list description defining informationmay be combined as one. In such implementations, the parameters fordefining a reference list description immediately follows the parametersfor defining the corresponding buffer description. In the example inFIG. 8A, the sequence of parameters becomes [number_of_bds=3], [BD0define], [RLD0 define], [BD1 define], [RLD1 define], [BD2 define], [RLD2define].

[Effect of Coding Method]

With the foregoing, the image coding apparatus 100 according to thisembodiment is capable of preventing redundant repetition of the sameparameters for constructing the reference lists in the coded bitstream.This allows the image coding apparatus 100 to improve the codingefficiency of the parameters describing reference list construction.Furthermore, the image coding apparatus 100 is capable of achievingdesign harmonization of reference list description data units with thebuffer description data units and with the hierarchically structuredsignaling units of a coded bitstream.

[Decoding Apparatus]

FIG. 10 is a block diagram which shows a structure of an image decodingapparatus 200 according to this embodiment.

The image decoding apparatus 200 shown in FIG. 10 decodes a codedbitstream 232 on a block-by-block basis, thereby generating decodedimage data 226. This image decoding apparatus 200 includes avariable-length decoding unit 212, an inverse quantization unit 204, aninverse orthogonal transformation unit 205, an adder 206, a block memory207, a frame memory 208, an intra prediction unit 209, an interprediction unit 210, a picture type determination unit 211, and a framememory control unit 213.

The coded bitstream 232 is, for example, the coded bitstream 132generated by the above image coding apparatus 100.

The variable-length decoding unit 212 performs variable-length decoding(entropy decoding) on the coded bitstream 232 to generate quantizedvalues 223 and frame memory control information 233. Here, the framememory control information 233 corresponds to the above frame memorycontrol information 133.

The inverse quantization unit 204 inversely quantizes the quantizedvalues 233, thereby generating frequency coefficients 224. The inverseorthogonal transformation unit 205 performs inverse frequency transformon the frequency coefficients 224, thereby generating prediction errordata 225. The adder 206 adds the prediction error data 225 and theprediction image data 231, thereby generating the decoded image data226. The decoded image data 226 is output from the image decodingapparatus 200 and, for example, is displayed.

The block memory 207 holds the decoded image data 226 as decoded imagedata 227 on a block-by-block basis. The frame memory 208 holds thedecoded image data 226 as decoded image data 228 on a frame-by-framebasis.

The intra prediction unit 209 performs intra prediction to generateprediction image data 229 of a current block to be decoded.Specifically, the intra prediction unit 209 searches within the decodedimage data 227 stored in the block memory 207, and estimates an imagearea which is most similar to the decoded image data 226.

The inter prediction unit 210 performs inter prediction using theper-frame decoded image data 228 stored in the frame memory 208, togenerate prediction image data 230 of the current block.

The picture type determination unit 211 selects one of the predictionimage data 229 and the prediction image data 230 and outputs theselected data as the prediction image data 231.

The frame memory control unit 213 manages the decoded image data 228stored in the frame memory 208. Specifically, the frame memory controlunit 213 performs memory management processes according to the framememory control information 223. Specifically, the frame memory controlunit 213 determines whether the decoded image data 128 is kept in theframe memory 208 or removed from the frame memory 208. Furthermore, theframe memory control unit 213 constructs reference lists to be used bythe inter prediction unit 210.

[Decoding Process]

Next, a description is given as to an image decoding method which isperformed by the image decoding apparatus 200 as mentioned above.

FIG. 11 is a flowchart of an image decoding method according to thisembodiment. Furthermore, FIG. 11 shows a decoding process which isperformed on a single video sequence including a plurality of pictures.

Firstly, the image decoding apparatus 200 obtains, from SPS in the codedbitstream 232, buffer description defining information which defines aplurality of buffer descriptions (S201). Next, the image decodingapparatus 200 obtains, from the above SPS, reference list descriptiondefining information which defines a plurality of reference listdescriptions (S202). Here, the reference list descriptions correspondone-to-one with the buffer descriptions.

Next, the image decoding apparatus 200 obtains buffer descriptionselecting information from a picture header (or a slice header) in thecoded bitstream 232 (S203). For the current picture (or slice), theimage decoding apparatus 200 then selects, out of the bufferdescriptions, one buffer description specified in the buffer descriptionselecting information (S204). Furthermore, the image decoding apparatus200 selects one reference list description corresponding to the selectedbuffer description.

Finally, the image decoding apparatus 200 decodes the current picture(or slice) using the selected buffer description and the selectedreference list description (S205).

The following describes a process of obtaining the reference listdescription defining information (S202) shown in FIG. 11 . FIG. 12 is aflowchart of a process of obtaining the reference list descriptiondefining information.

In this embodiment, the reference list description defining informationis obtained from SPS of the coded bitstream 232 in this obtainingprocess.

Firstly, the image decoding apparatus 200 obtains, from the SPS, a firstreordering flag included in the reference list description defininginformation (S212). The first reordering flag indicates whether or notreference list reordering is performed. Next, the image decodingapparatus 200 judges using the first reordering flag whether or notreference list reordering is performed (S213).

When reference list reordering is performed (Yes in S213), the imagedecoding apparatus 200 obtains, from SPS, first reference listreordering information included in the reference list descriptiondefining information (S214) and terminates the process of obtaining thereference list determination defining information (S202). The firstreference list reordering information indicates the details ofreordering of the picture identifiers included in the reference list.

On the other hand, when reference list reordering is not performed (Noin S213), the image decoding apparatus 200 terminates the process ofobtaining the reference list description defining information (S202).

The following describes a decoding process (S205) shown in FIG. 11 .FIG. 13 is a flowchart which shows a first embodiment of the decodingprocess (S205).

Firstly, the image decoding apparatus 200 constructs a default referencelist comprising all picture identifiers in the buffer descriptionaccording to a default reference list constructing scheme (S221). Next,the image decoding apparatus 200 judges using a first reordering flagwhether or not reference list reordering is performed (S222).

When reference list reordering is performed (Yes in S223), the imagedecoding apparatus 200 reorders the picture identifiers in the referencelist according to the first reference list reordering information(S224). The image decoding apparatus 200 then decodes the currentpicture or slice using the reordered reference list (S225).

On the other hand, when reference list reordering is not performed, theimage decoding apparatus 200 decodes the current picture or slice usingthe default reference list (S225).

FIG. 14 is a flowchart which shows a second embodiment of the decodingprocess (S205).

Firstly, the image decoding apparatus 200 constructs a default referencelist comprising all picture identifiers in the buffer descriptionaccording to a default reference list constructing scheme (S231). Next,the image decoding apparatus 200 obtains, from a slice header of thecurrent slice, an update flag for indicating whether or not a referencelist description is updated (S232). The image decoding apparatus 200then judges using the obtained update flag whether or not a referencelist description is updated (S233).

When a reference list description is updated (Yes in S234), the imagedecoding apparatus 200 obtains, from the slice header of the currentslice, a second reordering flag for indicating whether or not referencelist reordering is performed (S235). The image decoding apparatus 200then judges using the obtained second reordering flag whether or notreference list reordering is performed (S236).

When reference list reordering is performed (Yes in S236), the imagedecoding apparatus 200 obtains second reference list reorderinginformation from the slice header for reordering picture identifiers inthe reference list (S237). The image decoding apparatus 200 thenreorders the picture identifiers in the reference list according to theobtained second reference list reordering information (S238). Next, theimage decoding apparatus 200 decodes the current slice using thereordered reference list (S242).

On the other hand, when a reference list description is not updated (Noin S234), the image decoding apparatus 200 judges using the firstreordering flag included in the reference list description defininginformation whether or not reference list reordering is performed (S239and S240).

When reference list reordering is performed (Yes in S240), the imagedecoding apparatus 200 reorders the picture identifiers in the referencelist according to the reference list reordering information included inthe reference list description defining information (S241). Next, theimage decoding apparatus 200 decodes the current slice using thereordered reference list (S242).

On the other hand, when reference list reordering is not performed (Noin S236 or No in S240), the image decoding apparatus 200 decodes thecurrent slice using the default reference list (S242).

[Effect of Decoding Method]

With the foregoing, the image decoding apparatus 200 according to thisembodiment is capable of decoding a coded bitstream which is coded inthe form of improved coding efficiency and harmonized design ofreference list description data.

Second Embodiment

This embodiment describes a variation of the above first embodiment. Theimage coding apparatus according to this embodiment further writes, intoPPS, buffer description updating information for modifying bufferdescriptions, and reference list description updating information formodifying reference list descriptions.

The following mainly describes differences from the first embodiment andthus omits overlapping explanations.

[Coding Apparatus]

The block diagram of the image coding apparatus 100 according to thisembodiment is the same or alike as that shown in FIG. 3 and therefore isnot explained.

[Coding Process]

The following describes an image coding method which is performed by theimage coding apparatus 100 according to this embodiment.

FIG. 15 is a flowchart of the image coding method according to thisembodiment. The processing shown in FIG. 15 additionally includes StepsS301 to S303 as compared to those shown in FIG. 4 in the image codingmethod according to the first embodiment.

After Step S103, the image coding apparatus 100 modifies a plurality ofbuffer descriptions and the corresponding reference list descriptions(S301). Specifically, the image coding apparatus 100 modifies one ormore buffer descriptions out of the plurality of buffer descriptions andthe reference list descriptions corresponding to the one or more bufferdescriptions. It is to be noted that the image coding apparatus 100 mayadd new buffer descriptions and the corresponding new reference listdescriptions instead of modifying the original buffer descriptions. Theimage coding apparatus 100 may modify some or all of the bufferdescriptions. For example, the image coding apparatus 100 may modifysome or all of the buffer elements included in the buffer descriptions.In this case, the image coding apparatus 100 modifies the part of thereference list descriptions corresponding to the modified part of thebuffer descriptions.

Next, in order to modify some buffer descriptions out of the pluralityof buffer descriptions, the image coding apparatus 100 writes, into PPSof the coded bitstream 132, buffer description updating informationwhich indicates the details of the modification (S302). Next, the imagecoding apparatus 100 writes, into the above PPS, reference listdescription updating information which defines the modified referencelist descriptions corresponding to the modified part of bufferdescriptions (S303). Here, each modified reference list descriptioncorresponds exclusively to one buffer description.

It is to be noted that, when new buffer descriptions and reference listdescriptions are determined to be created in Step S301, the bufferdescription updating information and the reference list descriptionupdating information comprise information for defining new additionalbuffer descriptions and the corresponding new reference listdescriptions.

When a modified buffer description is selected, reference listdescription updating information is written in Step S303. By so doing,the modified reference list description replaces (overrides) thereference list description defined in the reference list descriptiondefining information.

Next, the image coding apparatus 100 selects one buffer description outof the modified plurality of buffer descriptions (S104) and writes, intothe picture header of the current picture in the coded bitstream 132,buffer description selecting information which specifies the selectedbuffer description (S105). Finally, the image coding apparatus 100 codesthe current picture or slice using the selected buffer description andthe corresponding reference list description (S106).

The details of Steps S103 and S106 are the same or alike as those shownin FIGS. 5 to 7 in the processing of the first embodiment.

The following describes a process of writing the reference listdescription updating information (S303). FIG. 16 is a flowchart of awriting process (S303) of reference list description updatinginformation. In this embodiment, the reference list description updatinginformation is written into PPS of the coded bitstream 132 in thiswriting process (S303).

Firstly, the image coding apparatus 100 determines which of a defaultreference list and a reordered reference list is used (S311). Next, theimage coding apparatus 100 writes, into PPS, a third reordering flag forindicating whether or not reference list reordering is performed (S312).The image coding apparatus 100 then judges using the written thirdreordering flag whether or not reference list reordering is performed(S313).

When reference list reordering is performed (Yes in S313), the imagecoding apparatus 100 writes, into PPS, third reference list reorderinginformation which indicates the details of the reordering, forreordering picture identifiers in a reference list (S314), andterminates the writing process (S303).

On the other hand, when reference list reordering is not performed (Noin S313), the image coding apparatus 100 terminates the writing process(S303).

Thus, the reference list description updating information includes thethird reordering flag and the third reference list reorderinginformation.

[Syntax Diagram]

FIGS. 17A and 17D are each a syntax diagram which shows the locations ofthe buffer description updating information and the reference listdescription updating information in a coded bitstream in thisembodiment. Two exemplary syntax locations are described in thefollowing.

A coded bitstream 132B shown in FIG. 17A is different from the codedbitstream 132 shown in FIG. 8A in that PPS 302B replaces PPS 302.Specifically, the PPS 302B further includes buffer description updatinginformation 323 (BD update) and reference list description updatinginformation 324 (RLD update).

The buffer description updating information 323 includesnumber-of-updates information 325 (number_of_bd_updates) and one or morepieces of updating information 326. Each piece of the updatinginformation 326 includes buffer description selecting information 327(bd_select) and buffer description modifying information 328 (BDmodify).

The number-of-updates information 325 (e.g. number_of_bd_updates=2)indicates the number of buffer descriptions to be modified and thenumber of corresponding reference list descriptions to be modified.

The buffer description selecting information 327 specifies a bufferdescription to be updated. The buffer description modifying information328 indicates the details of modification of the buffer description.

The reference list description updating information 324 includes one ormore pieces of reference list defining information 329 (RLD define).Each piece of the reference list defining information 329 defines thereference list description corresponding to the updated bufferdescription.

In a coded bitstream 132C shown in FIG. 17B, the PPS selectinginformation 333 and the buffer description selecting information 334 arenot included in the picture header 331A, but are included in the sliceheader 341. Also in this case, the effects the same as those in the caseshown in FIG. 17A can be obtained.

The buffer description updating information 323 and the reference listdescription updating information 324 may be located in signalling unitsother than PPS in a coded bitstream. Such other signalling units possessthe same characteristics as PPS in that they contain the parameters usedin common by a plurality of slices in one or more pictures. Theextension and adaptation from PPS to these other signalling units willbe apparent to those skilled in the art.

The above buffer description updating information and reference listdescription updating information are signalled in the sequence parameterset syntax structure according to the pseudo code in the table shown inFIG. 18 .

The semantics of the descriptors is the same as that in FIG. 9 .

The semantics associated with the syntax elements representing thebuffer description updating information is specified in the following.

number_of_bd_updates specifies the number of times the syntax elementbd_select is present in PPS. In other words, number_of_bd_updatesrepresents the number of buffer descriptions to be modified by PPS.

bd_select specifies an index into the lists BDDeltaPOC and BDTemporalIDrepresenting the buffer description BD[bd_select] to be modified by PPS.

bd_modification_operation specifies a modification operation to beapplied on the selected buffer description BD[bd_select].bd_modification_operation equal to 0 specifies the end of the loop formodifying the buffer description BD[bd_select].bd_modification_operation shall not be equal to 0 immediately followingthe syntax element bd_select.

In this embodiment, while bd_modification_operation equal to 1 specifiesthat a buffer element indicated by be_idx_in_bd_update in the bufferdescription BD[bd_select] is to be assigned a POC difference value to acurrent picture. This POC difference value replaces the existing storedPOC difference value.

In alternative implementations, additional buffer descriptionmodification operations indicated by bd_modification_operation may bedefined. One example is the operation for assigning marking for apicture indicated by a buffer element as a short term or long termreference picture. Another example is the operation for defining newadditional buffer description. In this case, bd_select specifies anindex to a plurality of new (non-existing) buffer descriptions andsubsequent buffer description modification operations assigns pictureindicators to the buffer elements in the new buffer descriptions.

be_idx_in_bd_update specifies the buffer element to be modified in thebuffer description BD[bd_select].

delta_poc_sign_flag specifies the sign (plus or minus) of the POCdifference between a current picture and the reference picture to beassociated with the buffer element BE[bd_select][be_idx_in_bd_update] inthe buffer description BD[bd_select]. delta_poc_sign_flag equal to 0specifies that the POC difference has a positive value, whiledelta_poc_sign_flag equal to 1 specifies that the POC difference has anegative value.

delta_poc_minus1 specifies an absolute POC difference value between acurrent picture and the reference picture to be associated with thebuffer element BE[bd_select][be_idx_in_bd_update] in the bufferdescription BD[bd_select]. first_delta_poc_sign_flag and first_delta_pocdefine the value of the signed variableBDDeltaPOC[bd_select][be_idx_in_bd_update] asBDDeltaPOC[bd_select][be_idx_in_bd_update]=(delta_poc_minus1+1)*(1−2*delta_poc_sign_flag)

temporal_id specifies a temporal identifier and is represented bybits_for_temporal_id bits. temporal_id defines the value of the unsignedvariable BDTemporalID[bd_select][be_idx_in_bd_update] asBDTemporalID[bd_select][be_idx_in_bd_update]=temporal_id

The semantics associated with the syntax elements representing thereference list description updating information is the same as thesemantics associated with the syntax elements representing the referencelist description defining information, as detailed in the previousdescription above. As mentioned above, when a buffer description ismodified by PPS, reference list description updating information iswritten to define a modified reference list description. The modifiedreference list description replaces (overrides) the initial referencelist description defined previously by the referred active SSP.

It is to be noted that the syntax loop describing buffer descriptionupdating information and reference list description updating informationmay be combined as one. In such implementations, the parameters fordefining a modified reference list description immediately follows theparameters for modifying the corresponding buffer description. In theexample in FIG. 17A, the sequence of parameters becomes[number_of_bd_updates=2], [bd_select=2], [BD2 modify], [RLD2 define],[bd_select=3], [BD3 modify], [RLD3 define].

[Effect of Coding Method]

With the foregoing, the image coding apparatus 100 according to thisembodiment is capable of preventing redundant repetition of the sameparameters for constructing the reference lists in the coded bitstream.This allows the image coding apparatus 100 to improve the codingefficiency of the parameters describing reference list construction.Furthermore, the image coding apparatus 100 is capable of achievingdesign harmonization of reference list description data units with thebuffer description data units and with the hierarchically structuredsignaling units of a coded bitstream.

[Decoding Apparatus]

The block diagram of the image decoding apparatus 200 according to thisembodiment is the same or alike as that shown in FIG. 10 and thereforeis not explained.

[Decoding Process]

The following describes an image decoding method which is performed bythe image decoding apparatus 200 according to this embodiment.

FIG. 19 is a flowchart of an image decoding method according to thisembodiment. The processing shown in FIG. 19 additionally includes StepsS401 and S402 as compared to those shown in FIG. 11 in the imagedecoding method according to the first embodiment.

After Step S202, the image decoding apparatus 200 obtains bufferdescription updating information from PPS of the coded bitstream 232 formodifying a plurality of buffer descriptions (S401). Next, the imagedecoding apparatus 200 obtains reference list description updatinginformation from the above PPS for defining a modified reference listdescription corresponding to the modified buffer description (S402).Here, each modified reference list description corresponds exclusivelyto one modified buffer description.

Next, the image decoding apparatus 200 obtains buffer descriptionselecting information from the picture header of the current picture inthe coded bitstream 232 for selecting one buffer description out of themodified plurality of buffer descriptions (S203). Next, the imagedecoding apparatus 200 selects, for the current picture (or slice), onebuffer description specified in the buffer description selectinginformation and one reference list description corresponding to thebuffer description (S204). Finally, the image decoding apparatus 200decodes the current picture or slice using the selected bufferdescription and the corresponding reference list description (S205).

The details of Steps S202 and S205 are the same or alike as those shownin FIGS. 12 to 14 in the processing of the first embodiment.

The following describes a process of obtaining the reference listdescription updating information (S402). FIG. 20 is a flowchart of aprocess of obtaining reference list description updating information(S402). In this embodiment, the reference list description updatinginformation is obtained from PPS of the coded bitstream 232 in theobtaining process (S402).

Firstly, the image decoding apparatus 200 obtains, from the referencelist description updating information, a third reordering flag forindicating whether or not reference list reordering is performed (S412).The image decoding apparatus 200 then judges using the obtained thirdreordering flag whether or not reference list reordering is performed(S413).

When reference list reordering is performed (Yes in S413), the imagedecoding apparatus 200 obtains, for reordering picture identifiers in areference list, reference list reordering information which indicatesthe details of the reordering (S414), and terminates the obtainingprocess (S402).

On the other hand, when reference list reordering is not performed (Noin S423), the image decoding apparatus 200 terminates the obtainingprocess (S402).

[Effect of Decoding Method]

With the foregoing, the image decoding apparatus 200 according to thisembodiment is capable of decoding a coded bitstream which is coded inthe form of improved coding efficiency and harmonized design ofreference list description data.

Third Embodiment

This embodiment describes a variation of the above second embodiment. Acoded bitstream in this embodiment is different from that in the secondembodiment in the structures of the buffer description updatinginformation and the reference list description updating information. Thefollowing mainly describes differences from the first or secondembodiment and thus omits overlapping explanations.

[Coding Apparatus]

The block diagram of the image coding apparatus 100 according to thisembodiment is the same or alike as that shown in FIG. 3 and therefore isnot explained.

[Coding Process]

The following describes an image coding method which is performed by theimage coding apparatus 100 according to this embodiment.

FIG. 21 is a flowchart of the image coding method according to thisembodiment. The processing shown in FIG. 21 additionally includes StepsS301A to S303A as compared to those shown in FIG. 4 in the image codingmethod according to the first embodiment. Furthermore, the processing inStep S105A is different from that in Step S105.

After Step S104, the image coding apparatus 100 determines modificationsfor the selected buffer description and the corresponding reference listdescription (S301A). The image coding apparatus 100 then writes, forselecting and modifying the selected buffer description, bufferdescription updating information which indicates the details of themodification (S302A), into PPS of the coded bitstream 132. Next, theimage coding apparatus 100 writes, into the above PPS, reference listdescription updating information which defines a modified reference listdescription corresponding to the selected buffer description (S303A).

Here, the buffer description updating information includes a parameterto indicate whether or not the selected buffer description is modified.When the selected buffer description is modified, a modified referencelist description is defined by the reference list updating information.This modified reference list description replaces the initial referencelist description corresponding to the selected buffer description. Whenthe selected buffer description is not modified, the reference listupdating information is not present in the above PPS and the initialreference list description corresponding to the selected bufferdescription applies.

Next, the image coding apparatus 100 writes PPS selecting informationinto a picture header of a current picture (or a slice header of acurrent slice) in the coded bitstream 132 for indicating that the abovePPS is referred by the picture (S105A). One corresponding bufferdescription and one corresponding reference list description are therebyreferred. Finally, the image coding apparatus 100 codes the currentpicture or slice using the selected buffer description and thecorresponding reference list description (S106).

The details of Steps S103 and S106 are the same or alike as those shownin FIGS. 5 to 7 in the processing of the first embodiment. The detailsof Step S303A are the same or alike as those shown in FIG. 16 in theprocessing of the second embodiment.

[Syntax Diagram]

FIGS. 22A and 22B are each a syntax diagram which shows the locations ofthe buffer description updating information and the reference listdescription updating information in a coded bitstream in exemplaryembodiments. Two exemplary syntax locations are described in thefollowing.

A coded bitstream 132D shown in FIG. 22A is different from the codedbitstream 132B shown in FIG. 17A in that buffer description updatinginformation 323D and reference list description updating information324D in PPS302D replace the buffer description updating information 323and the reference list description updating information 324 in PPS 302B.Furthermore, a picture header 331D is different from the picture header331.

The buffer description updating information 323D includes bufferdescription selecting information 351 (e.g. bd_select=2) to specify oneselected buffer description and a buffer description modifying flag 352(e.g. modify_flag=1) indicating whether or not the selected bufferdescription and the reference list description corresponding to theselected buffer description are to be modified. When the bufferdescription modifying flag 352 indicates that modification is performed,the buffer description updating information 323D further includes thebuffer description modifying information 328 (BD modify). Furthermore,when the buffer description modifying flag 352 indicates thatmodification is performed, the PPS 302B includes the reference listdescription updating information 324D including the reference listdefining information 329 (RLD define) which defines the modifiedreference list. On the other hand, when the buffer description modifyingflag 352 indicates that modification is not performed, the PPS302D doesnot include the buffer description modifying information 328 and thereference list defining information 329.

It is to be noted that the picture header 331D does not include thebuffer description selecting information 334.

With the foregoing, the PPS 302D is identified by the PPS identifier 322(e.g. pps_id=0) and is referred in the picture header 331D using the PPSselecting information 333 (e.g. pps_select=0). When the PPS 302D isreferred, the selected buffer description and the associated referencelist description are also referred. Slices (or sub-picture units) in thecurrent picture are coded or decoded using ordered reference picturesaccording to the selected buffer description and the selected referencelist description.

In a coded bitstream 132E shown in FIG. 22B, the PPS selectinginformation 333 is not included in the picture header 331A, but isincluded in a slice header 341E. Also in this case, the effects the sameas those in the case shown in FIG. 22A can be obtained.

It is to be noted that the buffer description updating information 323Dand the reference list description updating information 324D may belocated in signalling units other than PPS in a coded bitstream.

The above buffer description defining information and reference listdescription defining information are signalled in the sequence parameterset syntax structure according to the pseudo code detailed in theprevious description above. The buffer description updating informationand reference list description updating information are signalled in thesequence parameter set syntax structure according to the pseudo code inthe table shown in FIG. 23 .

The semantics of the descriptors is the same as that in FIG. 9 .

The semantics associated with the syntax elements representing thebuffer description updating information is specified in the following.

bd_select specifies an index into the lists BDDeltaPOC and BDTemporalIDrepresenting the buffer description BD[bd_select] to be referred to andoptionally be modified by PPS.

The semantics of bd_modification_operation, be_idx_in_bd_update,delta_poc_sign_flag, delta_poc_minus1, first_delta_poc_sign_flag,first_delta_poc, and temporal_id is the same as those in FIG. 18 .

The semantics associated with the syntax elements representing thereference list description updating information is the same as thesemantics associated with the syntax elements representing the referencelist description defining information, as detailed in the previousdescription above. When the selected buffer description is not modifiedas indicated by the internal variable IsBDModified not equal to 1, thesyntax elements representing the reference list description updatinginformation are not present in PPS, and the initial reference listdescription written in SPS is used. When the selected buffer descriptionis modified, the reference list description updating information iswritten into PPS for defining the modified reference lists which replacethe initial reference lists previously defined in SPS.

[Effect of Coding Method]

With the foregoing, the image coding apparatus 100 according to thisembodiment is capable of preventing redundant repetition of the sameparameters for constructing the reference lists in the coded bitstream.This allows the image coding apparatus 100 to improve the codingefficiency of the parameters describing reference list construction.Furthermore, the image coding apparatus 100 is capable of achievingdesign harmonization of reference list description data units with thebuffer description data units and with the hierarchically structuredsignaling units of a coded bitstream.

[Decoding Apparatus]

The block diagram of the image decoding apparatus 200 according to thisembodiment is the same or alike as that shown in FIG. 10 and thereforeis not explained.

[Decoding Process]

The following describes an image decoding method which is performed bythe image decoding apparatus 200 according to this embodiment.

FIG. 24 is a flowchart of the image decoding method according to thisembodiment. The processing shown in FIG. 24 additionally includes StepsS401A and S402 as compared to that shown in FIG. 11 in the imagedecoding method according to the first embodiment. Furthermore, theprocessing in Steps S203A and S204A is different from that in Steps S203and S204.

After Step S202, the image decoding apparatus 200 obtains bufferdescription selecting information and buffer description updatinginformation from PPS of the coded bitstream for selecting and modifyingone buffer description out of the plurality of buffer descriptions(S401A). Next, the image decoding apparatus 200 obtains, from the abovePPS, reference list description updating information for defining amodified reference list description corresponding to the selected bufferdescription (S402).

Next, the image decoding apparatus 200 obtains, from the picture headerof the current picture in the coded bitstream, a PPS identifier forindicating that the above PPS is referred by the current picture(S203A). Next, the image decoding apparatus 200 selects, for the currentpicture (or slice), one buffer description specified in the bufferdescription selecting information in PPS specified by the PPSidentifier, and one reference list description corresponding to thebuffer description (S204A). Finally, the image decoding apparatus 200decodes the current picture or slice using the selected bufferdescription and the corresponding reference list description (S205).

The details of Steps S202 and S205 are the same or alike as those shownin FIGS. 12 to 14 in the processing of the first embodiment. The detailsof Step S402 are the same or alike as those shown in FIG. 20 in theprocessing of the second embodiment.

[Effect of Decoding Method]

With the foregoing, the image decoding apparatus 200 according to thisembodiment is capable of decoding a coded bitstream which is coded inthe form of improved coding efficiency and harmonized design ofreference list description data.

Fourth Embodiment

This embodiment describes a variation of the above third embodiment. Inthis embodiment, the buffer description updating information and thereference list description updating information are included in theslice header. The following mainly describes differences from the first,second, or third embodiment and thus omits overlapping explanations.

[Coding Apparatus]

The block diagram of the image coding apparatus 100 according to thisembodiment is the same or alike as that shown in FIG. 3 and therefore isnot explained.

[Coding Process]

The following describes an image coding method which is performed by theimage coding apparatus 100 according to this embodiment.

FIG. 26 is a flowchart of the image decoding method according to thisembodiment. The processing shown in FIG. 25 includes Steps S3028 andS3038 instead of Steps S302A, S303A, and S105A shown in FIG. 21 in theimage coding method according to the third embodiment.

After Step S301A, the image coding apparatus 100 writes, for modifyingthe selected buffer description, buffer description selectinginformation, which specifies the selected buffer description, and bufferdescription updating information, into the slice header of the currentslice in the coded bitstream (S302B). Next, the image coding apparatus100 writes, into the slice header, reference list description updatinginformation which defines a modified reference list descriptioncorresponding to the selected buffer description (S303B).

In this implementation, the buffer description updating informationincludes a parameter to indicate whether or not the selected bufferdescription is modified. When the selected buffer description ismodified, the reference list updating information defines a modifiedreference list description. This modified reference list descriptionreplaces the initial reference list description corresponding to theselected buffer description. When the selected buffer description is notmodified, the reference list updating information is not present in theslice header and the initial reference list description corresponding tothe selected buffer description applies.

Finally, the image coding apparatus 100 codes the current slice usingthe selected buffer description and the corresponding reference listdescription (S106).

The details of Steps S103 and S106 are the same or alike as those shownin FIGS. 5 and 6 in the processing of the first embodiment. The detailsof Step S303B are the same or alike as the processing resulting fromchanging, from PPS to a slice header, where to write the thirdreordering flag and the third reference list reordering information inthe processing shown in FIG. 16 in the second embodiment.

[Syntax Diagram]

FIG. 26 is a syntax diagram which shows the locations of the bufferdescription updating information and the reference list descriptionupdating information in a coded bitstream in this embodiment.

A coded bitstream 132F shown in FIG. 26 is different from the codedbitstream 132E shown in FIG. 22B in that the buffer description updatinginformation 323D and the reference list description updating information324D are included not in the PPS 302D, but in the slice header 341E.

When the buffer description modifying flag 352 indicates thatmodification is performed, the buffer description updating information323D further includes the buffer description modifying information 328.Furthermore, when the buffer description modifying flag 352 indicatesthat modification is performed, a slice header 341F includes thereference list description updating information 324D including thereference list defining information 329 (RLD define) which defines themodified reference list. On the other hand, when the buffer descriptionmodifying flag 352 indicates that modification is not performed, theslice header 341F does not include the buffer description modifyinginformation 328 and the reference list defining information 329.

Slices (or sub-picture units) in the current picture are coded ordecoded using ordered reference pictures according to the selectedbuffer description and the selected reference list description.

The above buffer description defining information and reference listdescription defining information are signalled in the sequence parameterset syntax structure according to the pseudo code detailed in theprevious description above. The buffer description updating informationand reference list description updating information are signalled in theslice header syntax structure according to the pseudo code in the tableshown in FIG. 27 .

The semantics of the descriptors is the same as that in FIG. 9 .

The semantics associated with the syntax elements representing thebuffer description updating information according to this embodiment isthe same as the semantics associated with the syntax elementsrepresenting the reference list description updating informationaccording to the third embodiment, as detailed in the previousdescription above.

The semantics associated with the syntax elements representing thereference list description updating information is the same as thesemantics associated with the syntax elements representing the referencelist description defining information, as detailed in the previousdescription above. When the selected buffer description is not modifiedas indicated by the internal variable IsBDModified not equal to 1, thesyntax elements representing the reference list description updatinginformation are not present in the slice header, and the initialreference list description written in SPS is used. When the selectedbuffer description is modified, the reference list updating informationin the slice header is written for defining the modified reference listswhich replace the initial reference lists previously defined in SPS.

[Effect of Coding Method]

With the foregoing, the image coding apparatus 100 according to thisembodiment is capable of preventing redundant repetition of the sameparameters for constructing the reference lists in the coded bitstream.This allows the image coding apparatus 100 to improve the codingefficiency of the parameters describing reference list construction.Furthermore, the image coding apparatus 100 is capable of achievingdesign harmonization of reference list description data units with thebuffer description data units and with the hierarchically structuredsignaling units of a coded bitstream.

[Decoding Apparatus]

The block diagram of the image decoding apparatus 200 according to thisembodiment is the same or alike as that shown in FIG. 10 and thereforeis not explained.

[Decoding Process]

The following describes an image decoding method which is performed bythe image decoding apparatus 200 according to this embodiment.

FIG. 28 is a flowchart of the image decoding method according to thisembodiment. The processing shown in FIG. 28 includes Steps S401B andS402B instead of Step S203 shown in FIG. 11 in the image decoding methodaccording to the first embodiment.

After Step S202, the image decoding apparatus 200 obtains bufferdescription selecting information and buffer description updatinginformation from the slice header of the current slice in the codedbitstream for selecting and modifying one buffer description out of theplurality of buffer descriptions (S401B). Next, the image decodingapparatus 200 obtains reference list description updating informationfrom the slice header for defining a modified reference list descriptioncorresponding to the selected buffer description (S402B).

Next, the image decoding apparatus 200 obtains the buffer descriptionindicated in the buffer description selecting information (S204).Finally, the image decoding apparatus 200 decodes the current sliceusing the selected buffer description and the corresponding referencelist description (S205).

The details of Steps S202 and S205 are the same or alike as those shownin FIGS. 12 and 13 in the processing of the first embodiment. Thedetails of Step S402 are the same or alike as those shown in FIG. 20 inthe processing of the second embodiment.

[Effect of Decoding Method]

With the foregoing, the image decoding apparatus 200 according to thisembodiment is capable of decoding a coded bitstream which is coded inthe form of improved coding efficiency and harmonized design ofreference list description data.

As above, in the image coding method according to this embodiment, thebuffer description defining information, which defines a plurality ofbuffer descriptions, and the reference list description defininginformation, which defines a plurality of reference list descriptionscorresponding to the buffer descriptions, are written into SPScorresponding to the coded bitstream.

Furthermore, in the image coding method, for each processing unit thatis a picture or a slice, one of the buffer descriptions is selected, andbuffer description selecting information which specifies the selectedbuffer description is written into a first header of the processing unitwhich is included in the coded bitstream. Here, the first header is aheader of a picture or a slice and specifically is PPS, a pictureheader, or a slice header.

In the image coding method, the processing unit is coded using theselected buffer description and the reference list description whichcorresponds to the selected buffer description.

By so doing, in the image coding method, the buffer description defininginformation and the reference list description defining information arewritten into the sequence parameter set shared by a plurality ofpictures, and a buffer description identifier indicating a bufferdescription to be selected is written into a header of each picture orslice. This allows a reduction in redundant information and therebyallows an improvement in coding efficiency in the image coding method ascompared to the case where the buffer description defining informationand the reference list description defining information are written intoa picture parameter set.

Furthermore, in the image coding method, at least one of the bufferdescriptions is modified, and buffer description updating information,which indicates the details of the modification, and reference listdescription updating information, which defines the reference listdescription corresponding to the modified buffer description, arewritten into a second header of the processing unit. Here, the secondheader is a header of a picture or a slice and specifically is PPS, apicture header, or a slice header.

In this case, in the image coding method, the processing unit is codedusing the modified buffer description and the reference list descriptionwhich corresponds to the modified buffer description.

By so doing, in the image coding method, the buffer description and thereference list description set in SPS can be updated for each picture orslice. Thus, the image coding method allows a reduction in redundantinformation and also allows, when necessary, the buffer description andthe reference list description to be modified for each picture or slice.

Although the image coding apparatus and the image decoding apparatusaccording to one or more aspects of the inventive concepts have beendescribed above, the herein disclosed subject matter is to be considereddescriptive and illustrative only.

For example, although the above describes an example in which SPS isincluded in the coded bitstream which includes slice data and the like,SPS may be transmitted from the image coding apparatus to the imagedecoding apparatus separately from the coded bitstream which includesthe slice data and the like.

Respective processing units included in the image coding apparatus andthe image decoding apparatus according to each of the above embodimentsare typically implemented as a large scale integration (LSI) that is anintegrated circuit. These processing units may be each provided on asingle chip, and part or all of them may be formed into a single chip.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. Field Programmable Gate Array (FPGA) that canbe programmed after manufacturing LSIs, or a reconfigurable processorthat allows re-configuration of the connection or configuration of anLSI can be used for the same purpose.

Each of the structural elements in each of the above-describedembodiments may be configured in the form of an exclusive hardwareproduct, or may be realized by executing a software program suitable forthe structural element. Each of the structural elements may be realizedby means of a program executing unit, such as a CPU and a processor,reading and executing the software program recorded on a recordingmedium such as a hard disk or a semiconductor memory.

Furthermore, the inventive concept may be implemented as the abovesoftware program and may also be implemented as a non-transitorycomputer-readable recording medium on which such a program is recorded.In addition, it goes without saying that such a program may bedistributed via a communication network such as the Internet.

The numerals herein are all given to specifically illustrate theinventive concept and therefore do not limit it.

The segmentation of the functional blocks in each block diagram is anexample, and some of the functional blocks may be implemented as onefunctional block while one functional block may be divided into pluralparts, or part of the function of one functional block may be shifted toanother function block. Furthermore, the functions of a plurality offunctional blocks which have similar functions may be processed inparallel or in time-sliced fashion by single hardware or software.

The processing order of the steps included in the above image coding ordecoding method are given to specifically illustrate the inventiveconcept and therefore may be any other order. Part of the above stepsmay be performed at the same time as (in parallel with) another step.

Fifth Embodiment

The processing described in each of embodiments can be simplyimplemented in an independent computer system, by recording, in arecording medium, a program for implementing the configurations of themoving picture coding method and the moving picture decoding methoddescribed in each of embodiments. The recording media may be anyrecording media as long as the program can be recorded, such as amagnetic disk, an optical disk, a magnetic optical disk, an IC card, anda semiconductor memory.

Hereinafter, the applications to the moving picture coding method andthe moving picture decoding method described in each of embodiments andsystems using thereof will be described. The system has a feature ofhaving an image coding and decoding apparatus that includes an imagecoding apparatus using the image coding method and an image decodingapparatus using the image decoding method. Other configurations in thesystem can be changed as appropriate depending on the cases.

FIG. 29 illustrates an overall configuration of a content providingsystem ex100 for implementing content distribution services. The areafor providing communication services is divided into cells of desiredsize, and base stations ex106, ex107, ex108, ex109, and ex110 which arefixed wireless stations are placed in each of the cells.

The content providing system ex100 is connected to devices, such as acomputer ex111, a personal digital assistant (PDA) ex112, a cameraex113, a cellular phone ex114 and a game machine ex115, via the Internetex101, an Internet service provider ex102, a telephone network ex104, aswell as the base stations ex106 to ex110, respectively.

However, the configuration of the content providing system ex100 is notlimited to the configuration shown in FIG. 29 , and a combination inwhich any of the elements are connected is acceptable. In addition, eachdevice may be directly connected to the telephone network ex104, ratherthan via the base stations ex106 to ex110 which are the fixed wirelessstations. Furthermore, the devices may be interconnected to each othervia a short distance wireless communication and others.

The camera ex113, such as a digital video camera, is capable ofcapturing video. A camera ex116, such as a digital camera, is capable ofcapturing both still images and video. Furthermore, the cellular phoneex114 may be the one that meets any of the standards such as GlobalSystem for Mobile Communications (GSM) (registered trademark), CodeDivision Multiple Access (CDMA), Wideband-Code Division Multiple Access(W-CDMA), Long Term Evolution (LTE), and High Speed Packet Access(HSPA). Alternatively, the cellular phone ex114 may be a PersonalHandyphone System (PHS).

In the content providing system ex100, a streaming server ex103 isconnected to the camera ex113 and others via the telephone network ex104and the base station ex109, which enables distribution of images of alive show and others. In such a distribution, content (for example,video of a music live show) captured by the user using the camera ex113is coded as described above in each of embodiments (i.e., the camerafunctions as the image coding apparatus according to an aspect of thepresent disclosure), and the coded content is transmitted to thestreaming server ex103. On the other hand, the streaming server ex103carries out stream distribution of the transmitted content data to theclients upon their requests. The clients include the computer ex111, thePDA ex112, the camera ex113, the cellular phone ex114, and the gamemachine ex115 that are capable of decoding the above-mentioned codeddata. Each of the devices that have received the distributed datadecodes and reproduces the coded data (i.e., functions as the imagedecoding apparatus according to an aspect of the present disclosure).

The captured data may be coded by the camera ex113 or the streamingserver ex103 that transmits the data, or the coding processes may beshared between the camera ex113 and the streaming server ex103.Similarly, the distributed data may be decoded by the clients or thestreaming server ex103, or the decoding processes may be shared betweenthe clients and the streaming server ex103. Furthermore, the data of thestill images and video captured by not only the camera ex113 but alsothe camera ex116 may be transmitted to the streaming server ex103through the computer ex111. The coding processes may be performed by thecamera ex116, the computer ex111, or the streaming server ex103, orshared among them.

Furthermore, the coding and decoding processes may be performed by anLSI ex500 generally included in each of the computer ex111 and thedevices. The LSI ex500 may be configured of a single chip or a pluralityof chips. Software for coding and decoding video may be integrated intosome type of a recording medium (such as a CD-ROM, a flexible disk, anda hard disk) that is readable by the computer ex111 and others, and thecoding and decoding processes may be performed using the software.

Furthermore, when the cellular phone ex114 is equipped with a camera,the video data obtained by the camera may be transmitted. The video datais data coded by the LSI ex500 included in the cellular phone ex114.

Furthermore, the streaming server ex103 may be composed of servers andcomputers, and may decentralize data and process the decentralized data,record, or distribute data.

As described above, the clients may receive and reproduce the coded datain the content providing system ex100. In other words, the clients canreceive and decode information transmitted by the user, and reproducethe decoded data in real time in the content providing system ex100, sothat the user who does not have any particular right and equipment canimplement personal broadcasting.

Aside from the example of the content providing system ex100, at leastone of the moving picture coding apparatus (image coding apparatus) andthe moving picture decoding apparatus (image decoding apparatus)described in each of embodiments may be implemented in a digitalbroadcasting system ex200 illustrated in FIG. 30 . More specifically, abroadcast station ex201 communicates or transmits, via radio waves to abroadcast satellite ex202, multiplexed data obtained by multiplexingaudio data and others onto video data. The video data is data coded bythe moving picture coding method described in each of embodiments (i.e.,data coded by the image coding apparatus according to an aspect of thepresent disclosure). Upon receipt of the multiplexed data, the broadcastsatellite ex202 transmits radio waves for broadcasting. Then, a home-useantenna ex204 with a satellite broadcast reception function receives theradio waves. Next, a device such as a television (receiver) ex300 and aset top box (STB) ex217 decodes the received multiplexed data, andreproduces the decoded data (i.e., functions as the image decodingapparatus according to an aspect of the present disclosure).

Furthermore, a reader/recorder ex218 (i) reads and decodes themultiplexed data recorded on a recording medium ex215, such as a DVD anda BD, or (i) codes video signals in the recording medium ex215, and insome cases, writes data obtained by multiplexing an audio signal on thecoded data. The reader/recorder ex218 can include the moving picturedecoding apparatus or the moving picture coding apparatus as shown ineach of embodiments. In this case, the reproduced video signals aredisplayed on the monitor ex219, and can be reproduced by another deviceor system using the recording medium ex215 on which the multiplexed datais recorded. It is also possible to implement the moving picturedecoding apparatus in the set top box ex217 connected to the cable ex203for a cable television or to the antenna ex204 for satellite and/orterrestrial broadcasting, so as to display the video signals on themonitor ex219 of the television ex300. The moving picture decodingapparatus may be implemented not in the set top box but in thetelevision ex300.

FIG. 31 illustrates the television (receiver) ex300 that uses the movingpicture coding method and the moving picture decoding method describedin each of embodiments. The television ex300 includes: a tuner ex301that obtains or provides multiplexed data obtained by multiplexing audiodata onto video data, through the antenna ex204 or the cable ex203, etc.that receives a broadcast; a modulation/demodulation unit ex302 thatdemodulates the received multiplexed data or modulates data intomultiplexed data to be supplied outside; and amultiplexing/demultiplexing unit ex303 that demultiplexes the modulatedmultiplexed data into video data and audio data, or multiplexes videodata and audio data coded by a signal processing unit ex306 into data.

The television ex300 further includes: a signal processing unit ex306including an audio signal processing unit ex304 and a video signalprocessing unit ex305 that decode audio data and video data and codeaudio data and video data, respectively (which function as the imagecoding apparatus and the image decoding apparatus according to theaspects of the present disclosure); and an output unit ex309 including aspeaker ex307 that provides the decoded audio signal, and a display unitex308 that displays the decoded video signal, such as a display.Furthermore, the television ex300 includes an interface unit ex317including an operation input unit ex312 that receives an input of a useroperation. Furthermore, the television ex300 includes a control unitex310 that controls overall each constituent element of the televisionex300, and a power supply circuit unit ex311 that supplies power to eachof the elements. Other than the operation input unit ex312, theinterface unit ex317 may include: a bridge ex313 that is connected to anexternal device, such as the reader/recorder ex218; a slot unit ex314for enabling attachment of the recording medium ex216, such as an SDcard; a driver ex315 to be connected to an external recording medium,such as a hard disk; and a modem ex316 to be connected to a telephonenetwork. Here, the recording medium ex216 can electrically recordinformation using a non-volatile/volatile semiconductor memory elementfor storage. The constituent elements of the television ex300 areconnected to each other through a synchronous bus.

First, the configuration in which the television ex300 decodesmultiplexed data obtained from outside through the antenna ex204 andothers and reproduces the decoded data will be described. In thetelevision ex300, upon a user operation through a remote controllerex220 and others, the multiplexing/demultiplexing unit ex303demultiplexes the multiplexed data demodulated by themodulation/demodulation unit ex302, under control of the control unitex310 including a CPU. Furthermore, the audio signal processing unitex304 decodes the demultiplexed audio data, and the video signalprocessing unit ex305 decodes the demultiplexed video data, using thedecoding method described in each of embodiments, in the televisionex300. The output unit ex309 provides the decoded video signal and audiosignal outside, respectively. When the output unit ex309 provides thevideo signal and the audio signal, the signals may be temporarily storedin buffers ex318 and ex319, and others so that the signals arereproduced in synchronization with each other. Furthermore, thetelevision ex300 may read multiplexed data not through a broadcast andothers but from the recording media ex215 and ex216, such as a magneticdisk, an optical disk, and a SD card. Next, a configuration in which thetelevision ex300 codes an audio signal and a video signal, and transmitsthe data outside or writes the data on a recording medium will bedescribed. In the television ex300, upon a user operation through theremote controller ex220 and others, the audio signal processing unitex304 codes an audio signal, and the video signal processing unit ex305codes a video signal, under control of the control unit ex310 using thecoding method described in each of embodiments. Themultiplexing/demultiplexing unit ex303 multiplexes the coded videosignal and audio signal, and provides the resulting signal outside. Whenthe multiplexing/demultiplexing unit ex303 multiplexes the video signaland the audio signal, the signals may be temporarily stored in thebuffers ex320 and ex321, and others so that the signals are reproducedin synchronization with each other. Here, the buffers ex318, ex319,ex320, and ex321 may be plural as illustrated, or at least one buffermay be shared in the television ex300. Furthermore, data may be storedin a buffer so that the system overflow and underflow may be avoidedbetween the modulation/demodulation unit ex302 and themultiplexing/demultiplexing unit ex303, for example.

Furthermore, the television ex300 may include a configuration forreceiving an AV input from a microphone or a camera other than theconfiguration for obtaining audio and video data from a broadcast or arecording medium, and may code the obtained data. Although thetelevision ex300 can code, multiplex, and provide outside data in thedescription, it may be capable of only receiving, decoding, andproviding outside data but not the coding, multiplexing, and providingoutside data.

Furthermore, when the reader/recorder ex218 reads or writes multiplexeddata from or on a recording medium, one of the television ex300 and thereader/recorder ex218 may decode or code the multiplexed data, and thetelevision ex300 and the reader/recorder ex218 may share the decoding orcoding.

As an example, FIG. 32 illustrates a configuration of an informationreproducing/recording unit ex400 when data is read or written from or onan optical disk. The information reproducing/recording unit ex400includes constituent elements ex401, ex402, ex403, ex404, ex405, ex406,and ex407 to be described hereinafter. The optical head ex401 irradiatesa laser spot in a recording surface of the recording medium ex215 thatis an optical disk to write information, and detects reflected lightfrom the recording surface of the recording medium ex215 to read theinformation. The modulation recording unit ex402 electrically drives asemiconductor laser included in the optical head ex401, and modulatesthe laser light according to recorded data. The reproductiondemodulating unit ex403 amplifies a reproduction signal obtained byelectrically detecting the reflected light from the recording surfaceusing a photo detector included in the optical head ex401, anddemodulates the reproduction signal by separating a signal componentrecorded on the recording medium ex215 to reproduce the necessaryinformation. The buffer ex404 temporarily holds the information to berecorded on the recording medium ex215 and the information reproducedfrom the recording medium ex215. The disk motor ex405 rotates therecording medium ex215. The servo control unit ex406 moves the opticalhead ex401 to a predetermined information track while controlling therotation drive of the disk motor ex405 so as to follow the laser spot.The system control unit ex407 controls overall the informationreproducing/recording unit ex400. The reading and writing processes canbe implemented by the system control unit ex407 using variousinformation stored in the buffer ex404 and generating and adding newinformation as necessary, and by the modulation recording unit ex402,the reproduction demodulating unit ex403, and the servo control unitex406 that record and reproduce information through the optical headex401 while being operated in a coordinated manner. The system controlunit ex407 includes, for example, a microprocessor, and executesprocessing by causing a computer to execute a program for read andwrite.

Although the optical head ex401 irradiates a laser spot in thedescription, it may perform high-density recording using near fieldlight.

FIG. 33 illustrates the recording medium ex215 that is the optical disk.On the recording surface of the recording medium ex215, guide groovesare spirally formed, and an information track ex230 records, in advance,address information indicating an absolute position on the diskaccording to change in a shape of the guide grooves. The addressinformation includes information for determining positions of recordingblocks ex231 that are a unit for recording data. Reproducing theinformation track ex230 and reading the address information in anapparatus that records and reproduces data can lead to determination ofthe positions of the recording blocks. Furthermore, the recording mediumex215 includes a data recording area ex233, an inner circumference areaex232, and an outer circumference area ex234. The data recording areaex233 is an area for use in recording the user data. The innercircumference area ex232 and the outer circumference area ex234 that areinside and outside of the data recording area ex233, respectively arefor specific use except for recording the user data. The informationreproducing/recording unit 400 reads and writes coded audio, coded videodata, or multiplexed data obtained by multiplexing the coded audio andvideo data, from and on the data recording area ex233 of the recordingmedium ex215.

Although an optical disk having a layer, such as a DVD and a BD isdescribed as an example in the description, the optical disk is notlimited to such, and may be an optical disk having a multilayerstructure and capable of being recorded on a part other than thesurface. Furthermore, the optical disk may have a structure formultidimensional recording/reproduction, such as recording ofinformation using light of colors with different wavelengths in the sameportion of the optical disk and for recording information havingdifferent layers from various angles.

Furthermore, a car ex210 having an antenna ex205 can receive data fromthe satellite ex202 and others, and reproduce video on a display devicesuch as a car navigation system ex211 set in the car ex210, in thedigital broadcasting system ex200. Here, a configuration of the carnavigation system ex211 will be a configuration, for example, includinga GPS receiving unit from the configuration illustrated in FIG. 31 . Thesame will be true for the configuration of the computer ex111, thecellular phone ex114, and others.

FIG. 34A illustrates the cellular phone ex114 that uses the movingpicture coding method and the moving picture decoding method describedin embodiments. The cellular phone ex114 includes: an antenna ex350 fortransmitting and receiving radio waves through the base station ex110; acamera unit ex365 capable of capturing moving and still images; and adisplay unit ex358 such as a liquid crystal display for displaying thedata such as decoded video captured by the camera unit ex365 or receivedby the antenna ex350. The cellular phone ex114 further includes: a mainbody unit including an operation key unit ex366; an audio output unitex357 such as a speaker for output of audio; an audio input unit ex356such as a microphone for input of audio; a memory unit ex367 for storingcaptured video or still pictures, recorded audio, coded or decoded dataof the received video, the still pictures, e-mails, or others; and aslot unit ex364 that is an interface unit for a recording medium thatstores data in the same manner as the memory unit ex367.

Next, an example of a configuration of the cellular phone ex114 will bedescribed with reference to FIG. 34B. In the cellular phone ex114, amain control unit ex360 designed to control overall each unit of themain body including the display unit ex358 as well as the operation keyunit ex366 is connected mutually, via a synchronous bus ex370, to apower supply circuit unit ex361, an operation input control unit ex362,a video signal processing unit ex355, a camera interface unit ex363, aliquid crystal display (LCD) control unit ex359, amodulation/demodulation unit ex352, a multiplexing/demultiplexing unitex353, an audio signal processing unit ex354, the slot unit ex364, andthe memory unit ex367.

When a call-end key or a power key is turned ON by a user's operation,the power supply circuit unit ex361 supplies the respective units withpower from a battery pack so as to activate the cell phone ex114.

In the cellular phone ex114, the audio signal processing unit ex354converts the audio signals collected by the audio input unit ex356 invoice conversation mode into digital audio signals under the control ofthe main control unit ex360 including a CPU, ROM, and RAM. Then, themodulation/demodulation unit ex352 performs spread spectrum processingon the digital audio signals, and the transmitting and receiving unitex351 performs digital-to-analog conversion and frequency conversion onthe data, so as to transmit the resulting data via the antenna ex350.Also, in the cellular phone ex114, the transmitting and receiving unitex351 amplifies the data received by the antenna ex350 in voiceconversation mode and performs frequency conversion and theanalog-to-digital conversion on the data. Then, themodulation/demodulation unit ex352 performs inverse spread spectrumprocessing on the data, and the audio signal processing unit ex354converts it into analog audio signals, so as to output them via theaudio output unit ex357.

Furthermore, when an e-mail in data communication mode is transmitted,text data of the e-mail inputted by operating the operation key unitex366 and others of the main body is sent out to the main control unitex360 via the operation input control unit ex362. The main control unitex360 causes the modulation/demodulation unit ex352 to perform spreadspectrum processing on the text data, and the transmitting and receivingunit ex351 performs the digital-to-analog conversion and the frequencyconversion on the resulting data to transmit the data to the basestation ex110 via the antenna ex350. When an e-mail is received,processing that is approximately inverse to the processing fortransmitting an e-mail is performed on the received data, and theresulting data is provided to the display unit ex358.

When video, still images, or video and audio in data communication modeis or are transmitted, the video signal processing unit ex355 compressesand codes video signals supplied from the camera unit ex365 using themoving picture coding method shown in each of embodiments, and transmitsthe coded video data to the multiplexing/demultiplexing unit ex353. Incontrast, during when the camera unit ex365 captures video, stillimages, and others, the audio signal processing unit ex354 codes audiosignals collected by the audio input unit ex356, and transmits the codedaudio data to the multiplexing/demultiplexing unit ex353.

The multiplexing/demultiplexing unit ex353 multiplexes the coded videodata supplied from the video signal processing unit ex355 and the codedaudio data supplied from the audio signal processing unit ex354, using apredetermined method. Then, the modulation/demodulation unit(modulation/demodulation circuit unit) ex352 performs spread spectrumprocessing on the multiplexed data, and the transmitting and receivingunit ex351 performs digital-to-analog conversion and frequencyconversion on the data so as to transmit the resulting data via theantenna ex350.

When receiving data of a video file which is linked to a Web page andothers in data communication mode or when receiving an e-mail with videoand/or audio attached, in order to decode the multiplexed data receivedvia the antenna ex350, the multiplexing/demultiplexing unit ex353demultiplexes the multiplexed data into a video data bit stream and anaudio data bit stream, and supplies the video signal processing unitex355 with the coded video data and the audio signal processing unitex354 with the coded audio data, through the synchronous bus ex370. Thevideo signal processing unit ex355 decodes the video signal using amoving picture decoding method corresponding to the moving picturecoding method shown in each of embodiments (i.e., functions as the imagedecoding apparatus according to the aspect of the present disclosure),and then the display unit ex358 displays, for instance, the video andstill images included in the video file linked to the Web page via theLCD control unit ex359. Furthermore, the audio signal processing unitex354 decodes the audio signal, and the audio output unit ex357 providesthe audio.

Furthermore, similarly to the television ex300, a terminal such as thecellular phone ex114 probably has 3 types of implementationconfigurations including not only (i) a transmitting and receivingterminal including both a coding apparatus and a decoding apparatus, butalso (ii) a transmitting terminal including only a coding apparatus and(iii) a receiving terminal including only a decoding apparatus. Althoughthe digital broadcasting system ex200 receives and transmits themultiplexed data obtained by multiplexing audio data onto video data inthe description, the multiplexed data may be data obtained bymultiplexing not audio data but character data related to video ontovideo data, and may be not multiplexed data but video data itself.

As such, the moving picture coding method and the moving picturedecoding method in each of embodiments can be used in any of the devicesand systems described. Thus, the advantages described in each ofembodiments can be obtained.

Furthermore, the inventive concept is not limited to each ofembodiments, and various modifications and revisions can be made in anyof the embodiments in the present disclosure.

Sixth Embodiment

Video data can be generated by switching, as necessary, between (i) themoving picture coding method or the moving picture coding apparatusshown in each of embodiments and (ii) a moving picture coding method ora moving picture coding apparatus in conformity with a differentstandard, such as MPEG-2, MPEG-4 AVC, and VC-1.

Here, when a plurality of video data that conforms to the differentstandards is generated and is then decoded, the decoding methods need tobe selected to conform to the different standards. However, since towhich standard each of the plurality of the video data to be decodedconforms cannot be detected, there is a problem that an appropriatedecoding method cannot be selected.

In order to solve the problem, multiplexed data obtained by multiplexingaudio data and others onto video data has a structure includingidentification information indicating to which standard the video dataconforms. The specific structure of the multiplexed data including thevideo data generated in the moving picture coding method and by themoving picture coding apparatus shown in each of embodiments will behereinafter described. The multiplexed data is a digital stream in theMPEG-2 Transport Stream format.

FIG. 35 illustrates a structure of the multiplexed data. As illustratedin FIG. 35 , the multiplexed data can be obtained by multiplexing atleast one of a video stream, an audio stream, a presentation graphicsstream (PG), and an interactive graphics stream. The video streamrepresents primary video and secondary video of a movie, the audiostream (IG) represents a primary audio part and a secondary audio partto be mixed with the primary audio part, and the presentation graphicsstream represents subtitles of the movie. Here, the primary video isnormal video to be displayed on a screen, and the secondary video isvideo to be displayed on a smaller window in the primary video.Furthermore, the interactive graphics stream represents an interactivescreen to be generated by arranging the GUI components on a screen. Thevideo stream is coded in the moving picture coding method or by themoving picture coding apparatus shown in each of embodiments, or in amoving picture coding method or by a moving picture coding apparatus inconformity with a conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1. The audio stream is coded in accordance with a standard, such asDolby-AC-3, Dolby Digital Plus, MLP, DTS, DTS-HD, and linear PCM.

Each stream included in the multiplexed data is identified by PID. Forexample, 0x1011 is allocated to the video stream to be used for video ofa movie, 0x1100 to 0x111F are allocated to the audio streams, 0x1200 to0x121F are allocated to the presentation graphics streams, 0x1400 to0x141F are allocated to the interactive graphics streams, 0x1B00 to0x1B1F are allocated to the video streams to be used for secondary videoof the movie, and 0x1A00 to 0x1A1F are allocated to the audio streams tobe used for the secondary audio to be mixed with the primary audio.

FIG. 36 schematically illustrates how data is multiplexed. First, avideo stream ex235 composed of video frames and an audio stream ex238composed of audio frames are transformed into a stream of PES packetsex236 and a stream of PES packets ex239, and further into TS packetsex237 and TS packets ex240, respectively. Similarly, data of apresentation graphics stream ex241 and data of an interactive graphicsstream ex244 are transformed into a stream of PES packets ex242 and astream of PES packets ex245, and further into TS packets ex243 and TSpackets ex246, respectively. These TS packets are multiplexed into astream to obtain multiplexed data ex247.

FIG. 37 illustrates how a video stream is stored in a stream of PESpackets in more detail. The first bar in FIG. 37 shows a video framestream in a video stream. The second bar shows the stream of PESpackets. As indicated by arrows denoted as yy1, yy2, yy3, and yy4 inFIG. 37 , the video stream is divided into pictures as I-pictures,B-pictures, and P-pictures each of which is a video presentation unit,and the pictures are stored in a payload of each of the PES packets.Each of the PES packets has a PES header, and the PES header stores aPresentation Time-Stamp (PTS) indicating a display time of the picture,and a Decoding Time-Stamp (DTS) indicating a decoding time of thepicture.

FIG. 38 illustrates a format of TS packets to be finally written on themultiplexed data. Each of the TS packets is a 188-byte fixed lengthpacket including a 4-byte TS header having information, such as a PIDfor identifying a stream and a 184-byte TS payload for storing data. ThePES packets are divided, and stored in the TS payloads, respectively.When a BD ROM is used, each of the TS packets is given a 4-byteTP_Extra_Header, thus resulting in 192-byte source packets. The sourcepackets are written on the multiplexed data. The TP_Extra_Header storesinformation such as an Arrival_Time_Stamp (ATS). The ATS shows atransfer start time at which each of the TS packets is to be transferredto a PID filter. The source packets are arranged in the multiplexed dataas shown at the bottom of FIG. 38 . The numbers incrementing from thehead of the multiplexed data are called source packet numbers (SPNs).

Each of the TS packets included in the multiplexed data includes notonly streams of audio, video, subtitles and others, but also a ProgramAssociation Table (PAT), a Program Map Table (PMT), and a Program ClockReference (PCR). The PAT shows what a PID in a PMT used in themultiplexed data indicates, and a PID of the PAT itself is registered aszero. The PMT stores PIDs of the streams of video, audio, subtitles andothers included in the multiplexed data, and attribute information ofthe streams corresponding to the PIDs. The PMT also has variousdescriptors relating to the multiplexed data. The descriptors haveinformation such as copy control information showing whether copying ofthe multiplexed data is permitted or not. The PCR stores STC timeinformation corresponding to an ATS showing when the PCR packet istransferred to a decoder, in order to achieve synchronization between anArrival Time Clock (ATC) that is a time axis of ATSs, and an System TimeClock (STC) that is a time axis of PTSs and DTSs.

FIG. 39 illustrates the data structure of the PMT in detail. A PMTheader is disposed at the top of the PMT. The PMT header describes thelength of data included in the PMT and others. A plurality ofdescriptors relating to the multiplexed data is disposed after the PMTheader. Information such as the copy control information is described inthe descriptors. After the descriptors, a plurality of pieces of streaminformation relating to the streams included in the multiplexed data isdisposed. Each piece of stream information includes stream descriptorseach describing information, such as a stream type for identifying acompression codec of a stream, a stream PID, and stream attributeinformation (such as a frame rate or an aspect ratio). The streamdescriptors are equal in number to the number of streams in themultiplexed data.

When the multiplexed data is recorded on a recording medium and others,it is recorded together with multiplexed data information files.

Each of the multiplexed data information files is management informationof the multiplexed data as shown in FIG. 40 . The multiplexed datainformation files are in one to one correspondence with the multiplexeddata, and each of the files includes multiplexed data information,stream attribute information, and an entry map.

As illustrated in FIG. 40 , the multiplexed data information includes asystem rate, a reproduction start time, and a reproduction end time. Thesystem rate indicates the maximum transfer rate at which a system targetdecoder to be described later transfers the multiplexed data to a PIDfilter. The intervals of the ATSs included in the multiplexed data areset to not higher than a system rate. The reproduction start timeindicates a PTS in a video frame at the head of the multiplexed data. Aninterval of one frame is added to a PTS in a video frame at the end ofthe multiplexed data, and the PTS is set to the reproduction end time.

As shown in FIG. 41 , a piece of attribute information is registered inthe stream attribute information, for each PID of each stream includedin the multiplexed data. Each piece of attribute information hasdifferent information depending on whether the corresponding stream is avideo stream, an audio stream, a presentation graphics stream, or aninteractive graphics stream. Each piece of video stream attributeinformation carries information including what kind of compression codecis used for compressing the video stream, and the resolution, aspectratio and frame rate of the pieces of picture data that is included inthe video stream. Each piece of audio stream attribute informationcarries information including what kind of compression codec is used forcompressing the audio stream, how many channels are included in theaudio stream, which language the audio stream supports, and how high thesampling frequency is. The video stream attribute information and theaudio stream attribute information are used for initialization of adecoder before the player plays back the information.

In the present embodiment, the multiplexed data to be used is of astream type included in the PMT. Furthermore, when the multiplexed datais recorded on a recording medium, the video stream attributeinformation included in the multiplexed data information is used. Morespecifically, the moving picture coding method or the moving picturecoding apparatus described in each of embodiments includes a step or aunit for allocating unique information indicating video data generatedby the moving picture coding method or the moving picture codingapparatus in each of embodiments, to the stream type included in the PMTor the video stream attribute information. With the configuration, thevideo data generated by the moving picture coding method or the movingpicture coding apparatus described in each of embodiments can bedistinguished from video data that conforms to another standard.

Furthermore, FIG. 42 illustrates steps of the moving picture decodingmethod according to the present embodiment. In Step exS100, the streamtype included in the PMT or the video stream attribute informationincluded in the multiplexed data information is obtained from themultiplexed data. Next, in Step exS101, it is determined whether or notthe stream type or the video stream attribute information indicates thatthe multiplexed data is generated by the moving picture coding method orthe moving picture coding apparatus in each of embodiments. When it isdetermined that the stream type or the video stream attributeinformation indicates that the multiplexed data is generated by themoving picture coding method or the moving picture coding apparatus ineach of embodiments, in Step exS102, decoding is performed by the movingpicture decoding method in each of embodiments. Furthermore, when thestream type or the video stream attribute information indicatesconformance to the conventional standards, such as MPEG-2, MPEG-4 AVC,and VC-1, in Step exS103, decoding is performed by a moving picturedecoding method in conformity with the conventional standards.

As such, allocating a new unique value to the stream type or the videostream attribute information enables determination whether or not themoving picture decoding method or the moving picture decoding apparatusthat is described in each of embodiments can perform decoding. Even whenmultiplexed data that conforms to a different standard is input, anappropriate decoding method or apparatus can be selected. Thus, itbecomes possible to decode information without any error. Furthermore,the moving picture coding method or apparatus, or the moving picturedecoding method or apparatus in the present embodiment can be used inthe devices and systems described above.

Seventh Embodiment

Each of the moving picture coding method, the moving picture codingapparatus, the moving picture decoding method, and the moving picturedecoding apparatus in each of embodiments is typically achieved in theform of an integrated circuit or a Large Scale Integrated (LSI) circuit.As an example of the LSI, FIG. 43 illustrates a configuration of the LSIex500 that is made into one chip. The LSI ex500 includes elements ex501,ex502, ex503, ex504, ex505, ex506, ex507, ex508, and ex509 to bedescribed below, and the elements are connected to each other through abus ex510. The power supply circuit unit ex505 is activated by supplyingeach of the elements with power when the power supply circuit unit ex505is turned on.

For example, when coding is performed, the LSI ex500 receives an AVsignal from a microphone ex117, a camera ex113, and others through an AVIO ex509 under control of a control unit ex501 including a CPU ex502, amemory controller ex503, a stream controller ex504, and a drivingfrequency control unit ex512. The received AV signal is temporarilystored in an external memory ex511, such as an SDRAM. Under control ofthe control unit ex501, the stored data is segmented into data portionsaccording to the processing amount and speed to be transmitted to asignal processing unit ex507. Then, the signal processing unit ex507codes an audio signal and/or a video signal. Here, the coding of thevideo signal is the coding described in each of embodiments.Furthermore, the signal processing unit ex507 sometimes multiplexes thecoded audio data and the coded video data, and a stream IO ex506provides the multiplexed data outside. The provided multiplexed data istransmitted to the base station ex107, or written on the recordingmedium ex215. When data sets are multiplexed, the data should betemporarily stored in the buffer ex508 so that the data sets aresynchronized with each other.

Although the memory ex511 is an element outside the LSI ex500, it may beincluded in the LSI ex500. The buffer ex508 is not limited to onebuffer, but may be composed of buffers. Furthermore, the LSI ex500 maybe made into one chip or a plurality of chips.

Furthermore, although the control unit ex501 includes the CPU ex502, thememory controller ex503, the stream controller ex504, the drivingfrequency control unit ex512, the configuration of the control unitex501 is not limited to such. For example, the signal processing unitex507 may further include a CPU. Inclusion of another CPU in the signalprocessing unit ex507 can improve the processing speed. Furthermore, asanother example, the CPU ex502 may serve as or be a part of the signalprocessing unit ex507, and, for example, may include an audio signalprocessing unit. In such a case, the control unit ex501 includes thesignal processing unit ex507 or the CPU ex502 including a part of thesignal processing unit ex507.

The name used here is LSI, but it may also be called IC, system LSI,super LSI, or ultra LSI depending on the degree of integration.

Moreover, ways to achieve integration are not limited to the LSI, and aspecial circuit or a general purpose processor and so forth can alsoachieve the integration. Field Programmable Gate Array (FPGA) that canbe programmed after manufacturing LSIs or a reconfigurable processorthat allows re-configuration of the connection or configuration of anLSI can be used for the same purpose.

In the future, with advancement in semiconductor technology, a brand-newtechnology may replace LSI. The functional blocks can be integratedusing such a technology. The possibility is that the present disclosureis applied to biotechnology.

Eighth Embodiment

When video data generated in the moving picture coding method or by themoving picture coding apparatus described in each of embodiments isdecoded, compared to when video data that conforms to a conventionalstandard, such as MPEG-2, MPEG-4 AVC, and VC-1 is decoded, theprocessing amount probably increases. Thus, the LSI ex500 needs to beset to a driving frequency higher than that of the CPU ex502 to be usedwhen video data in conformity with the conventional standard is decoded.However, when the driving frequency is set higher, there is a problemthat the power consumption increases.

In order to solve the problem, the moving picture decoding apparatus,such as the television ex300 and the LSI ex500 is configured todetermine to which standard the video data conforms, and switch betweenthe driving frequencies according to the determined standard. FIG. 44illustrates a configuration ex800 in the present embodiment. A drivingfrequency switching unit ex803 sets a driving frequency to a higherdriving frequency when video data is generated by the moving picturecoding method or the moving picture coding apparatus described in eachof embodiments. Then, the driving frequency switching unit ex803instructs a decoding processing unit ex801 that executes the movingpicture decoding method described in each of embodiments to decode thevideo data. When the video data conforms to the conventional standard,the driving frequency switching unit ex803 sets a driving frequency to alower driving frequency than that of the video data generated by themoving picture coding method or the moving picture coding apparatusdescribed in each of embodiments. Then, the driving frequency switchingunit ex803 instructs the decoding processing unit ex802 that conforms tothe conventional standard to decode the video data.

More specifically, the driving frequency switching unit ex803 includesthe CPU ex502 and the driving frequency control unit ex512 in FIG. 43 .Here, each of the decoding processing unit ex801 that executes themoving picture decoding method described in each of embodiments and thedecoding processing unit ex802 that conforms to the conventionalstandard corresponds to the signal processing unit ex507 in FIG. 43 .The CPU ex502 determines to which standard the video data conforms.Then, the driving frequency control unit ex512 determines a drivingfrequency based on a signal from the CPU ex502. Furthermore, the signalprocessing unit ex507 decodes the video data based on the signal fromthe CPU ex502. For example, the identification information described inthe sixth embodiment is probably used for identifying the video data.The identification information is not limited to the one described inthe sixth embodiment but may be any information as long as theinformation indicates to which standard the video data conforms. Forexample, when which standard video data conforms to can be determinedbased on an external signal for determining that the video data is usedfor a television or a disk, etc., the determination may be made based onsuch an external signal. Furthermore, the CPU ex502 selects a drivingfrequency based on, for example, a look-up table in which the standardsof the video data are associated with the driving frequencies as shownin FIG. 46 . The driving frequency can be selected by storing thelook-up table in the buffer ex508 and in an internal memory of an LSI,and with reference to the look-up table by the CPU ex502.

FIG. 45 illustrates steps for executing a method in the presentembodiment. First, in Step exS200, the signal processing unit ex507obtains identification information from the multiplexed data. Next, inStep exS201, the CPU ex502 determines whether or not the video data isgenerated by the coding method and the coding apparatus described ineach of embodiments based on the identification information. When thevideo data is generated by the moving picture coding method and themoving picture coding apparatus described in each of embodiments, inStep exS202, the CPU ex502 transmits a signal for setting the drivingfrequency to a higher driving frequency to the driving frequency controlunit ex512. Then, the driving frequency control unit ex512 sets thedriving frequency to the higher driving frequency. On the other hand,when the identification information indicates that the video dataconforms to the conventional standard, such as MPEG-2, MPEG-4 AVC, andVC-1, in Step exS203, the CPU ex502 transmits a signal for setting thedriving frequency to a lower driving frequency to the driving frequencycontrol unit ex512. Then, the driving frequency control unit ex512 setsthe driving frequency to the lower driving frequency than that in thecase where the video data is generated by the moving picture codingmethod and the moving picture coding apparatus described in each ofembodiments.

Furthermore, along with the switching of the driving frequencies, thepower conservation effect can be improved by changing the voltage to beapplied to the LSI ex500 or an apparatus including the LSI ex500. Forexample, when the driving frequency is set lower, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set to a voltage lower than that in the case where the drivingfrequency is set higher.

Furthermore, when the processing amount for decoding is larger, thedriving frequency may be set higher, and when the processing amount fordecoding is smaller, the driving frequency may be set lower as themethod for setting the driving frequency. Thus, the setting method isnot limited to the ones described above. For example, when theprocessing amount for decoding video data in conformity with MPEG-4 AVCis larger than the processing amount for decoding video data generatedby the moving picture coding method and the moving picture codingapparatus described in each of embodiments, the driving frequency isprobably set in reverse order to the setting described above.

Furthermore, the method for setting the driving frequency is not limitedto the method for setting the driving frequency lower. For example, whenthe identification information indicates that the video data isgenerated by the moving picture coding method and the moving picturecoding apparatus described in each of embodiments, the voltage to beapplied to the LSI ex500 or the apparatus including the LSI ex500 isprobably set higher. When the identification information indicates thatthe video data conforms to the conventional standard, such as MPEG-2,MPEG-4 AVC, and VC-1, the voltage to be applied to the LSI ex500 or theapparatus including the LSI ex500 is probably set lower. As anotherexample, when the identification information indicates that the videodata is generated by the moving picture coding method and the movingpicture coding apparatus described in each of embodiments, the drivingof the CPU ex502 does not probably have to be suspended. When theidentification information indicates that the video data conforms to theconventional standard, such as MPEG-2, MPEG-4 AVC, and VC-1, the drivingof the CPU ex502 is probably suspended at a given time because the CPUex502 has extra processing capacity. Even when the identificationinformation indicates that the video data is generated by the movingpicture coding method and the moving picture coding apparatus describedin each of embodiments, in the case where the CPU ex502 has extraprocessing capacity, the driving of the CPU ex502 is probably suspendedat a given time. In such a case, the suspending time is probably setshorter than that in the case where when the identification informationindicates that the video data conforms to the conventional standard,such as MPEG-2, MPEG-4 AVC, and VC-1.

Accordingly, the power conservation effect can be improved by switchingbetween the driving frequencies in accordance with the standard to whichthe video data conforms. Furthermore, when the LSI ex500 or theapparatus including the LSI ex500 is driven using a battery, the batterylife can be extended with the power conservation effect.

Ninth Embodiment

There are cases where a plurality of video data that conforms todifferent standards, is provided to the devices and systems, such as atelevision and a cellular phone. In order to enable decoding theplurality of video data that conforms to the different standards, thesignal processing unit ex507 of the LSI ex500 needs to conform to thedifferent standards. However, the problems of increase in the scale ofthe circuit of the LSI ex500 and increase in the cost arise with theindividual use of the signal processing units ex507 that conform to therespective standards.

In order to solve the problem, what is conceived is a configuration inwhich the decoding processing unit for implementing the moving picturedecoding method described in each of embodiments and the decodingprocessing unit that conforms to the conventional standard, such asMPEG-2, MPEG-4 AVC, and VC-1 are partly shared. Ex900 in FIG. 47A showsan example of the configuration. For example, the moving picturedecoding method described in each of embodiments and the moving picturedecoding method that conforms to MPEG-4 AVC have, partly in common, thedetails of processing, such as entropy coding, inverse quantization,deblocking filtering, and motion compensated prediction. The details ofprocessing to be shared probably include use of a decoding processingunit ex902 that conforms to MPEG-4 AVC. In contrast, a dedicateddecoding processing unit ex901 is probably used for other processingunique to an aspect of the present disclosure. Since the aspect of thepresent disclosure is characterized by frame memory control inparticular, for example, the dedicated decoding processing unit ex901 isused for frame memory control. Otherwise, the decoding processing unitis probably shared for one of the entropy decoding, deblockingfiltering, and motion compensation, or all of the processing. Thedecoding processing unit for implementing the moving picture decodingmethod described in each of embodiments may be shared for the processingto be shared, and a dedicated decoding processing unit may be used forprocessing unique to that of MPEG-4 AVC.

Furthermore, ex1000 in FIG. 47B shows another example in that processingis partly shared. This example uses a configuration including adedicated decoding processing unit ex1001 that supports the processingunique to an aspect of the present disclosure, a dedicated decodingprocessing unit ex1002 that supports the processing unique to anotherconventional standard, and a decoding processing unit ex1003 thatsupports processing to be shared between the moving picture decodingmethod according to the aspect of the present disclosure and theconventional moving picture decoding method. Here, the dedicateddecoding processing units ex1001 and ex1002 are not necessarilyspecialized for the processing according to the aspect of the presentdisclosure and the processing of the conventional standard,respectively, and may be the ones capable of implementing generalprocessing. Furthermore, the configuration of the present embodiment canbe implemented by the LSI ex500.

As such, reducing the scale of the circuit of an LSI and reducing thecost are possible by sharing the decoding processing unit for theprocessing to be shared between the moving picture decoding methodaccording to the aspect of the present disclosure and the moving picturedecoding method in conformity with the conventional standard.

Although the image coding apparatus and the image decoding apparatusaccording to one or more aspects of the inventive concepts have beendescribed above, the herein disclosed subject matter is to be considereddescriptive and illustrative only. Those skilled in the art will readilyappreciate that the appended Claims are of a scope intended to cover andencompass not only the particular embodiments disclosed, but alsoequivalent structures, methods, and/or uses which are obtained by makingvarious modifications in the embodiments and by arbitrarily combiningthe structural elements in different embodiments, without materiallydeparting from the principles and spirit of the inventive concept.

INDUSTRIAL APPLICABILITY

One or more exemplary embodiments disclosed herein are applicable toimage coding methods, image decoding methods, image coding apparatuses,and image decoding apparatuses. The image coding method, the imagedecoding method, the image coding apparatus, and the image decodingapparatus consistent with one or more exemplary embodiments of thepresent disclosure can be used for information display devices andimaging devices with high resolution which include televisions, digitalvideo recorders, car navigation systems, cellular phones, digitalcameras, and digital video cameras.

The invention claimed is:
 1. A method for transmitting a bitstream vianetwork, the method comprising: transmitting the bitstream via network,wherein the bitstream is generated by performing the steps of: writing,into a sequence header, (i) buffer descriptions, each of the bufferdescriptions specifying reference pictures to be held in a buffer forencoding the pictures and (ii) reference list descriptions whichcorrespond one-to-one with the buffer descriptions, each of thereference list descriptions indicating a correspondence relationshipbetween one of the reference pictures that is specified by acorresponding one of the buffer descriptions and an index foridentifying the reference picture; writing, into a header of one ofslices in one of the pictures, selecting information indicating one ofthe buffer descriptions; and (i) specifying one of the referencepictures held in the buffer using the buffer description indicated bythe selecting information, (ii) encoding the one of the slices using thespecified reference picture, and (iii) writing, into the encodedsequence, the encoded slice and the index that identifies the specifiedreference picture in the reference list description that corresponds tothe buffer description indicated by the selecting information, whereinsyntax elements included in the sequence header are applied to all ofthe pictures in the encoded sequence, the syntax elements included inthe sequence header including the buffer descriptions and the referencelist descriptions, and wherein syntax elements included in a header ofeach of the slices are applied to all blocks in the slice, the syntaxelements included in the header of the one of the slices including theselecting information.
 2. A non-transitory computer-readable mediumstoring a bitstream and computer executable instructions, which whenexecuted by a computer, cause the computer to transmit the bitstream viaa network, the bitstream being generated by the computer by performingthe steps of: writing, into a sequence header, (i) buffer descriptions,each of the buffer descriptions specifying reference pictures to be heldin a buffer for encoding the pictures and (ii) reference listdescriptions which correspond one-to-one with the buffer descriptions,each of the reference list descriptions indicating a correspondencerelationship between one of the reference pictures that is specified bya corresponding one of the buffer descriptions and an index foridentifying the reference picture; writing, into a header of one ofslices in one of the pictures, selecting information indicating one ofthe buffer descriptions; and (i) specifying one of the referencepictures held in the buffer using the buffer description indicated bythe selecting information, (ii) encoding the one of the slices using thespecified reference picture, and (iii) writing, into the encodedsequence, the encoded slice and the index that identifies the specifiedreference picture in the reference list description that corresponds tothe buffer description indicated by the selecting information, whereinsyntax elements included in the sequence header are applied to all ofthe pictures in the encoded sequence, the syntax elements included inthe sequence header including the buffer descriptions and the referencelist descriptions, and wherein syntax elements included in a header ofeach of the slices are applied to all blocks in the slice, the syntaxelements included in the header of the one of the slices including theselecting information.